We used high-resolution glass capillary columns to study the trimethylsilyl derivatives of some acidic metabolites found in pooled urine specimens form control and postpartum subjects. About 30 compounds were identified by gas chromatography-mass spectrometry-computer techniques. In general, open tubular capillary columns effect better resolution of trimethylsilyl derivatives of organic acids than do conventional packed columns. GESE-30 proved to be a good general-purpose stationary phase, whereas OV-17 offered certain advantages in resolving aromatic acid components.