Urine was collected for microscopy and culture by standard use of sterile adhesive bags and by extraction from wet disposable nappies from 45 patients aged 1 to 23 months. Urine can readily be obtained by compression of wet nappy fibres within a 20 ml syringe if highly absorbent brands that contain gel beads are avoided. Red and white cell numbers were reduced on light microscopy of specimens obtained from nappies, but bacterial counts were unchanged. On culture, 6 children were shown to have urinary tract infections by both methods; of the children who did not have a urine infection, the contamination rate was lower from nappy collections (10/39 vs 17/39 from urine bags). Biochemical analysis of urine collected from 11 older children showed very close correlation for sodium, potassium, urea, and creatinine concentrations and osmolality between freshly voided urine and samples obtained after they were soaked into disposable nappies for 3 h and reclaimed, although there was greater variation for measurements of calcium and phosphate. Extraction of urine from disposable nappies put on within 4 h and which are not soiled by faeces is an inexpensive, rapid, and simple method to collect urine from young children for culture, microscopy for bacteria, and biochemical analysis.