diff --git a/reasoning_gym/arithmetic/__init__.py b/reasoning_gym/arithmetic/__init__.py
index 999b4521..05d321da 100644
--- a/reasoning_gym/arithmetic/__init__.py
+++ b/reasoning_gym/arithmetic/__init__.py
@@ -5,6 +5,7 @@ Arithmetic tasks for training reasoning capabilities:
 from .basic_arithmetic import BasicArithmeticDataset, BasicArithmeticDatasetConfig
 from .calendar_arithmetic import CalendarArithmeticConfig, CalendarArithmeticDataset
 from .chain_sum import ChainSum, ChainSumConfig
+from .count_bits import CountBitsConfig, CountBitsDataset
 from .fraction_simplification import FractionSimplificationConfig, FractionSimplificationDataset
 from .gcd import GCDConfig, GCDDataset
 from .gsm_symbolic.gsm_symbolic import GSMSymbolicDataset, GSMSymbolicDatasetConfig
@@ -35,4 +36,6 @@ __all__ = [
     "GSMSymbolicDataset",
     "TimeIntervalsConfig",
     "TimeIntervalsDataset",
+    "CountBitsConfig",
+    "CountBitsDataset",
 ]
diff --git a/reasoning_gym/arithmetic/count_bits.py b/reasoning_gym/arithmetic/count_bits.py
new file mode 100644
index 00000000..5dc2c099
--- /dev/null
+++ b/reasoning_gym/arithmetic/count_bits.py
@@ -0,0 +1,47 @@
+"""Count number of 1 bits in a number."""
+
+from dataclasses import dataclass
+from random import Random
+from typing import Optional
+
+from ..factory import ProceduralDataset, register_dataset
+
+QUESTION_TEMPLATE = """How many 1 bits are there in the binary representation of the number {number}?"""
+
+
+@dataclass
+class CountBitsConfig:
+    """Configuration for Count Bits dataset generation"""
+
+    max_n: int = 2**31 - 1  # Maximum number to consider
+
+    size: int = 500  # Virtual dataset size
+    seed: Optional[int] = None
+
+    def validate(self):
+        """Validate configuration parameters"""
+        assert 1 <= self.max_n, "max_n must be at least 1"
+
+
+class CountBitsDataset(ProceduralDataset):
+    """Generates Count Bits exercises with configurable difficulty"""
+
+    def __init__(self, config: CountBitsConfig):
+        super().__init__(config=config, seed=config.seed, size=config.size)
+
+    def __getitem__(self, idx: int) -> dict:
+        """Generate a single Count Bits question"""
+        rng = Random(self.seed + idx)
+
+        number = rng.randint(1, self.config.max_n)
+        binary = bin(number)[2:]
+        answer = binary.count("1")
+
+        return {
+            "question": QUESTION_TEMPLATE.format(number=number),
+            "answer": str(answer),
+            "metadata": {"number": number, "solution": answer, "binary": binary},
+        }
+
+
+register_dataset("count_bits", CountBitsDataset, CountBitsConfig)
diff --git a/tests/test_count_bits.py b/tests/test_count_bits.py
new file mode 100644
index 00000000..6a36c886
--- /dev/null
+++ b/tests/test_count_bits.py
@@ -0,0 +1,83 @@
+"""Tests for Count bits questions generation"""
+
+import pytest
+
+from reasoning_gym.arithmetic.count_bits import CountBitsConfig, CountBitsDataset
+
+
+def test_count_bits_config_validation():
+    """Test that invalid configs raise appropriate errors"""
+    with pytest.raises(AssertionError):
+        config = CountBitsConfig(max_n=-1)  # Negative not allowed
+        config.validate()
+
+    with pytest.raises(AssertionError):
+        config = CountBitsConfig(max_n=0)  # Zero not allowed
+        config.validate()
+
+
+def test_count_bits_dataset_deterministic():
+    """Test that dataset generates same items with same seed"""
+    config = CountBitsConfig(seed=42, size=10)
+    dataset1 = CountBitsDataset(config)
+    dataset2 = CountBitsDataset(config)
+
+    for i in range(len(dataset1)):
+        assert dataset1[i] == dataset2[i]
+
+
+def test_count_bits_dataset_items():
+    """Test basic properties of generated items"""
+    config = CountBitsConfig(max_n=10, size=10, seed=42)
+    dataset = CountBitsDataset(config)
+
+    for i in range(len(dataset)):
+        item = dataset[i]
+        # Check item structure
+        assert isinstance(item, dict)
+        assert "question" in item
+        assert "answer" in item
+        assert "metadata" in item
+
+        # Check metadata
+        assert "number" in item["metadata"]
+        assert "solution" in item["metadata"]
+        assert "binary" in item["metadata"]
+
+        number = item["metadata"]["number"]
+        solution = item["metadata"]["solution"]
+        binary = item["metadata"]["binary"]
+
+        # Verify values
+        assert number <= config.max_n
+        assert solution >= 0
+        assert set(binary) <= {"0", "1"}
+
+
+def test_count_bits_dataset_iteration():
+    """Test that iteration respects dataset size"""
+    config = CountBitsConfig(size=5, seed=42)
+    dataset = CountBitsDataset(config)
+
+    items = list(dataset)
+    assert len(items) == config.size
+
+    # Test multiple iterations yield same items
+    assert items == list(dataset)
+
+
+def test_count_bits_answer():
+    """Verify the number of 1 bits in the binary representation of a number"""
+    config = CountBitsConfig(size=5, seed=42)
+    dataset = CountBitsDataset(config)
+
+    for item in dataset:
+        number = item["metadata"]["number"]
+        solution = item["metadata"]["solution"]
+
+        # Count number of 1 bits in the number by shifting
+        count = 0
+        while number:
+            count += number & 1
+            number >>= 1
+        assert solution == count