diff --git a/CHANGELOG.md b/CHANGELOG.md
index 947e8f9a..bb74fac7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,11 +1,14 @@
 # 0.1.2 2024-XX-XX
 
+- Transpose default chunk sizes to 1000 variants and 10,000 samples (issue:300)
+
+- Add chunksize options to mkschema (issue:294)
+
 Breaking changes
 
 - ICF metadata format version bumped to ensure long-term compatility between numpy 1.26.x
   and numpy >= 2. Existing ICFs will need to be recreated.
 
-- Add chunksize options to mkschema (issue:294)
 
 # 0.1.1 2024-06-19
 
diff --git a/bio2zarr/vcf2zarr/vcz.py b/bio2zarr/vcf2zarr/vcz.py
index 3094b233..0cf25ca5 100644
--- a/bio2zarr/vcf2zarr/vcz.py
+++ b/bio2zarr/vcf2zarr/vcz.py
@@ -235,11 +235,10 @@ def fromjson(s):
     def generate(icf, variants_chunk_size=None, samples_chunk_size=None):
         m = icf.num_records
         n = icf.num_samples
-        # FIXME
         if samples_chunk_size is None:
-            samples_chunk_size = 1000
+            samples_chunk_size = 10_000
         if variants_chunk_size is None:
-            variants_chunk_size = 10_000
+            variants_chunk_size = 1000
         logger.info(
             f"Generating schema with chunks={variants_chunk_size, samples_chunk_size}"
         )
diff --git a/tests/test_vcz.py b/tests/test_vcz.py
index 6787461f..789fd59a 100644
--- a/tests/test_vcz.py
+++ b/tests/test_vcz.py
@@ -74,7 +74,12 @@ def test_not_enough_memory_for_two(
         other_zarr_path = tmp_path / "zarr"
         with caplog.at_level("WARNING"):
             vcf2zarr.encode(
-                icf_path, other_zarr_path, max_memory=max_memory, worker_processes=2
+                icf_path,
+                other_zarr_path,
+                max_memory=max_memory,
+                worker_processes=2,
+                samples_chunk_size=1000,
+                variants_chunk_size=10_000,
             )
         assert "Limiting number of workers to 1 to keep within" in caplog.text
         ds1 = sg.load_dataset(zarr_path)
@@ -164,6 +169,12 @@ def test_chunk_sizes(self, icf_path, samples_chunk_size, variants_chunk_size):
                 found += 1
         assert found > 0
 
+    def test_default_chunk_size(self, icf_path):
+        icf = vcf2zarr.IntermediateColumnarFormat(icf_path)
+        schema = vcf2zarr.VcfZarrSchema.generate(icf)
+        assert schema.samples_chunk_size == 10_000
+        assert schema.variants_chunk_size == 1000
+
 
 class TestSchemaJsonRoundTrip:
     def assert_json_round_trip(self, schema):
@@ -297,8 +308,8 @@ def test_format_version(self, schema):
         assert schema.format_version == vcz_mod.ZARR_SCHEMA_FORMAT_VERSION
 
     def test_chunk_size(self, schema):
-        assert schema.samples_chunk_size == 1000
-        assert schema.variants_chunk_size == 10000
+        assert schema.samples_chunk_size == 10000
+        assert schema.variants_chunk_size == 1000
 
     def test_samples(self, schema):
         assert schema.asdict()["samples"] == [
@@ -322,7 +333,7 @@ def test_variant_contig(self, schema):
             "name": "variant_contig",
             "dtype": "i1",
             "shape": (9,),
-            "chunks": (10000,),
+            "chunks": (1000,),
             "dimensions": ("variants",),
             "description": "An identifier from the reference genome or an "
             "angle-bracketed ID string pointing to a contig in the assembly file",
@@ -342,7 +353,7 @@ def test_call_genotype(self, schema):
             "name": "call_genotype",
             "dtype": "i1",
             "shape": (9, 3, 2),
-            "chunks": (10000, 1000, 2),
+            "chunks": (1000, 10000, 2),
             "dimensions": ("variants", "samples", "ploidy"),
             "description": "",
             "vcf_field": None,
@@ -361,7 +372,7 @@ def test_call_genotype_mask(self, schema):
             "name": "call_genotype_mask",
             "dtype": "bool",
             "shape": (9, 3, 2),
-            "chunks": (10000, 1000, 2),
+            "chunks": (1000, 10000, 2),
             "dimensions": ("variants", "samples", "ploidy"),
             "description": "",
             "vcf_field": None,
@@ -380,7 +391,7 @@ def test_call_genotype_phased(self, schema):
             "name": "call_genotype_mask",
             "dtype": "bool",
             "shape": (9, 3, 2),
-            "chunks": (10000, 1000, 2),
+            "chunks": (1000, 10000, 2),
             "dimensions": ("variants", "samples", "ploidy"),
             "description": "",
             "vcf_field": None,
@@ -399,7 +410,7 @@ def test_call_GQ(self, schema):
             "name": "call_GQ",
             "dtype": "i1",
             "shape": (9, 3),
-            "chunks": (10000, 1000),
+            "chunks": (1000, 10000),
             "dimensions": ("variants", "samples"),
             "description": "Genotype Quality",
             "vcf_field": "FORMAT/GQ",