1. In man, the antidepressant agent 3-(3-methylphenyl)-5-hydroxymethyl-2-oxazolidinone (toloxatone) on oral dosing was mainly eliminated in urine (80% dose in 12 h). 2. Plasma concn. of total radioactivity was max (5.8 micrograms equiv./ml) at 30 min to 1 h after administration and declined rapidly (t1/2, 1.25 h). Unchanged drug accounted for 48, 32 and 13% of plasma radioactivity at 15 min, 1 h and 6 h, respectively. 3. The drug was extensively metabolized. The major urinary metabolites were 3-(3-carboxyphenyl)-5-hydroxymethyl-2-oxazolidinone and a glucuronide of toloxatone. A minor urinary metabolite, characterized as a phenolic derivative, was also excreted conjugated.