Urinary component level was examined by proton nuclear magnetic resonance (¹H-NMR) spectroscopy 2-3 days before mating, on day 17-19 of pregnancy and on day 9-11 of lactation in SHN female mice. Urinary levels of taurine and betaine, both of which were found in milk, continued to decline through pregnancy and lactation. Creatinine and creatine decreased and increased, respectively, in the middle of lactation. Allantoin also increased at the end of pregnancy. There was little difference in the levels of urea and lactic acid at any stage examined. Concurrent pregnancy affected little any component level in the middle of lactation. Among correlations between reproductive parameters and urinary component levels, litter size on the day of parturition and total pup weight on day 12 of lactation had the positive and the negative correlations with urinary levels of lactic acid and taurine, respectively. The significance of these findings was considered and the possibility that the measurement of urinary components by ¹H-NMR is a useful method to estimate the metabolic change of small experimental animals during reproduction was provided.