1. Urinary levels of xylitol and glucuronic, glucaric, gulonic and ascorbic acids were measured in the rat, rabbit, guinea-pig and marmoset by an improved g.l.c. technique. 2. Administration of a compound (2-methylbenzanilide) known to be conjugated and excreted as a beta-glucuronide had some effect on the output of these compounds of the glucuronic acid pathway in all four species, and caused a significant decrease in gulonic acid in the rat.