A colorimetric method for the determination of vitamin B6 has been used to study the urinary excretion of the vitamin in the rat. At high dose levels (10 mg per kg and above) 50 to 70% of the vitamin is excreted by both normal and deficient rats. The vitamin is rapidly and completely absorbed and is rapidly excreted. At low levels (2 mg per kg) the data are qualitative, but normal rats appear to excrete a higher percentage of the ingested vitamin than B6–deficient rats.