diff --git a/larray/core/axis.py b/larray/core/axis.py
index 2d8f81baa..5ae80ab03 100644
--- a/larray/core/axis.py
+++ b/larray/core/axis.py
@@ -1349,10 +1349,13 @@ def to_hdf(self, filepath, key=None):
                 raise ValueError("Argument key must be provided explicitly in case of anonymous axis")
             key = self.name
         key = _translate_group_key_hdf(key)
-        s = pd.Series(data=self.labels, name=self.name)
+        dtype_kind = self.labels.dtype.kind
+        data = np.char.encode(self.labels, 'utf-8') if dtype_kind == 'U' else self.labels
+        s = pd.Series(data=data, name=self.name)
         with LHDFStore(filepath) as store:
             store.put(key, s)
             store.get_storer(key).attrs.type = 'Axis'
+            store.get_storer(key).attrs.dtype_kind = dtype_kind
             store.get_storer(key).attrs.wildcard = self.iswildcard
 
     @property
diff --git a/larray/core/group.py b/larray/core/group.py
index 52030d474..6d93c9e9f 100644
--- a/larray/core/group.py
+++ b/larray/core/group.py
@@ -1462,10 +1462,15 @@ def to_hdf(self, filepath, key=None, axis_key=None):
             if self.axis.name is None:
                 raise ValueError("Argument axis_key must be provided explicitly if the associated axis is anonymous")
             axis_key = self.axis.name
-        s = pd.Series(data=self.eval(), name=self.name)
+        data = self.eval()
+        dtype_kind = data.dtype.kind if isinstance(data, np.ndarray) else ''
+        if dtype_kind == 'U':
+            data = np.char.encode(data, 'utf-8')
+        s = pd.Series(data=data, name=self.name)
         with LHDFStore(filepath) as store:
             store.put(key, s)
             store.get_storer(key).attrs.type = 'Group'
+            store.get_storer(key).attrs.dtype_kind = dtype_kind
             if axis_key not in store:
                 self.axis.to_hdf(store, key=axis_key)
             store.get_storer(key).attrs.axis_key = axis_key
diff --git a/larray/inout/hdf.py b/larray/inout/hdf.py
index 025498add..09ea6d0c7 100644
--- a/larray/inout/hdf.py
+++ b/larray/inout/hdf.py
@@ -88,15 +88,21 @@ def read_hdf(filepath_or_buffer, key, fill_value=nan, na=nan, sort_rows=False, s
                 name = str(pd_obj.name)
             if name == 'None':
                 name = None
-            res = Axis(labels=pd_obj.values, name=name)
+            labels = pd_obj.values
+            if 'dtype_kind' in attrs and attrs['dtype_kind'] == 'U':
+                labels = np.char.decode(labels, 'utf-8')
+            res = Axis(labels=labels, name=name)
             res._iswildcard = attrs['wildcard']
         elif _type == 'Group':
             if name is None:
                 name = str(pd_obj.name)
             if name == 'None':
                 name = None
+            key = pd_obj.values
+            if 'dtype_kind' in attrs and attrs['dtype_kind'] == 'U':
+                key = np.char.decode(key, 'utf-8')
             axis = read_hdf(filepath_or_buffer, attrs['axis_key'])
-            res = LGroup(key=pd_obj.values, name=name, axis=axis)
+            res = LGroup(key=key, name=name, axis=axis)
     return res
 
 
diff --git a/larray/tests/test_array.py b/larray/tests/test_array.py
index 4d669d2ca..268e73f72 100644
--- a/larray/tests/test_array.py
+++ b/larray/tests/test_array.py
@@ -1,3 +1,4 @@
+# -*- coding: utf8 -*-
 from __future__ import absolute_import, division, print_function
 
 import os
diff --git a/larray/tests/test_axis.py b/larray/tests/test_axis.py
index 87ed1de75..1410e9e26 100644
--- a/larray/tests/test_axis.py
+++ b/larray/tests/test_axis.py
@@ -1,4 +1,6 @@
+# -*- coding: utf8 -*-
 from __future__ import absolute_import, division, print_function
+
 import pytest
 import os.path
 import numpy as np
@@ -391,6 +393,7 @@ def test_h5_io(tmpdir):
     lipro = Axis('lipro=P01..P05')
     anonymous = Axis(range(3))
     wildcard = Axis(3, 'wildcard')
+    string_axis = Axis(['@!àéè&%µ$~', '/*-+_§()><', 'another label'], 'string_axis')
     fpath = os.path.join(str(tmpdir), 'axes.h5')
 
     # ---- default behavior ----
@@ -410,6 +413,10 @@ def test_h5_io(tmpdir):
     wildcard2 = read_hdf(fpath, key=wildcard.name)
     assert wildcard2.iswildcard
     assert wildcard.equals(wildcard2)
+    # string axis
+    string_axis.to_hdf(fpath)
+    string_axis2 = read_hdf(fpath, string_axis.name)
+    assert string_axis.equals(string_axis2)
 
     # ---- specific key ----
     # int axis
diff --git a/larray/tests/test_group.py b/larray/tests/test_group.py
index fba0c5ad6..9fd582bab 100644
--- a/larray/tests/test_group.py
+++ b/larray/tests/test_group.py
@@ -1,4 +1,6 @@
+# -*- coding: utf8 -*-
 from __future__ import absolute_import, division, print_function
+
 import pytest
 import os.path
 import numpy as np
@@ -192,6 +194,7 @@ def test_h5_io_lgroup(tmpdir):
     named_axis_not_in_file = lipro['P01,P03,P05'] >> 'P_odd'
     anonymous = age[':5']
     wildcard = age_wildcard[':5'] >> 'age_w_05'
+    string_group = Axis(['@!àéè&%µ$~', '/*-+_§()><', 'another label'], 'string_axis')[:] >> 'string_group'
 
     # ---- default behavior ----
     # named group
@@ -209,6 +212,10 @@ def test_h5_io_lgroup(tmpdir):
     named_axis_not_in_file.to_hdf(fpath)
     named2 = read_hdf(fpath, key=named_axis_not_in_file.name)
     assert all(named_axis_not_in_file == named2)
+    # string group
+    string_group.to_hdf(fpath)
+    string_group2 = read_hdf(fpath, key=string_group.name)
+    assert all(string_group == string_group2)
 
     # ---- specific hdf group + key ----
     hdf_group = 'my_groups'