Serotonin receptors were examined in various brain regions of female rats 24 hours after treatment with 25, 50 or 75 mg/kg chlordecone. With each dose of chlordecone, there was a significant reduction in the specific binding of 3H-5-HT to striatum. Binding to cortex, hippocampus, hypothalamus, midbrain or brainstem did not systematically vary as a function of treatment conditions. Tremor developed in chlordecone treated female rats in a dose dependent manner with 25 mg/kg producing only slight tremor. Moderate to severe tremor was evident in rats given 75 mg/kg chlordecone. These findings support previous indications that chlordecone's action on the striatal serotoninergic system in an important component in its induction of tremor. Most such studies, however, have used relatively high doses of chlordecone so it has been difficult to determine if the serotoninergic change preceded or resulted from the tremor. The significant decrease in serotonin receptors at a dose of chlordecone which led to only slight tremor suggest that the serotoninergic change may be causally related to the production of the tremor.