The DDT syndrome in rats consists of tremor, myoclonus, running seizures, hyperthermia, episodic boxing, and excessive grooming. DDT did not change whole-brain glycine levels when the rats had stimulus-sensitive myoclonus, spontaneous myoclonus, or seizures. However, regional analysis showed a decrease in glycine levels in the pons and medulla initially, but they rose again despite worsening of the myoclonus. Glycine given intraventricularly and the glycine prodrug, milacemide, given intraperitoneally suppressed DDT-induced myoclonus. A dose of milacemide that prevented DDT-induced myoclonus caused a significant increase in glycine levels in cortex, septum accumbens, cerebellum, striatum, hypocampus, diencephalon, midbrain, pons, and medulla. The increase was most marked in the forebrain structures. There was no change in serine levels in these areas. These data suggest that the glycinergic system may be playing an important role in the manifestation of DDT-induced myoclonus.