With a new enzymatic test using oxalate oxidase, serum and urinary oxalate can easily and quickly be determined. Serum oxalate in females was significantly higher than in males (39.5 mumol/l, 30.8 mumol/l). Increased serum levels were found only in male patients. Urinary excretion did not reveal sex-dependent differences in healthy persons. The normal range of oxalate excretion in 104 adult healthy persons was 83-365 mumol/day (95% quartile). In 130 stone formers (nonrecurrent and recurrent group) urinary oxalate excretion was found to be in the normal range. Evaluation of urinary oxalate concentration in morning samples showed increased levels in both groups of male stone formers. Oxalate concentration was unaltered in female patients.