The rates of distribution of the radioactive precursor label de novo and of the reutilization pathways of inosine monophosphate biosynthesis between adenine and guanine nucleotides in the acid-soluble fraction and RNA from chicken liver were determined. The activity of enzymes involved in inosine monophosphate conversion into adenine or guanine nucleotides or in uric acid biosynthesis was determined. It was shown that in chicken liver the activity of IMP-dehydrogenase and the rate constant for the label ([14C]glycine) incorporation into the guanine nucleotide pool is 3.5 times as high as that of adenyl succinate synthetase and the rate constant for the label liberation into the adenine nucleotide pool. The rate of xanthine synthesis is by one order of magnitude more than that of hypoxanthine and uric acid. The rate of IMP synthesis from [14C]hypoxanthine via the guanine nucleotide pathway is also higher in this case. Hence, in chicken liver IMP oxidation to XMP seems to proceed with a high efficiency and can thus be used, in addition to dephosphorylation, for ammonia extrusion.