Hyperglycinemia was induced by dipropylacetate (DPA) (dose 14-41 mg/kg per day) in 10 Finnish epileptic patients with neurologically disabling diseases of various kinds. When comparing the levels of glycine in plasma, cerebrospinal fluid and urine from the patients with 10 otherwise comparable patients, and normal values there was a fourfold excretion of glycine in urine. All the treated patients had elevated CSF (49 +/- 23 mumol/l) and plasma (475 +/- 76 mumol/l) glycine concentrations. The plasma/CSF glycine ratio was not influenced by the treatment. In comparison with corresponding values in nonketotic hyperglycinemia and ketotic hyperglycinemia, this condition probably arises in a manner similar to secondary hyperglycinemia in organic aciduria. DPA probably influences metabolism in a way similar to some metabolites of amino acids in organic acidurias.