14C-Tricycloquinazoline (TCQ) was slowly eliminated following i.p. injection into mice and this may be related to its rapid uptake by adipose tissue. Metabolites were principally excreted in faeces and only trace amounts of radioactivity were detected in urine. 1-Hydroxy-TCQ and 3-hydroxy-TCQ were identified, but these accounted for less than 1 per cent of the faecal radioactivity, which was mainly associated with polar substances resulting from extensive degradation of TCQ. 1-Hydroxy-TCQ and 3-hydroxy-TCQ were also identified as biliary metabolites and were formed following in vitro incubation of 14C-TCQ with mouse liver homogenates. The major metabolites in each case, however, were unidentified polar compounds. © 1968.