Studies were made on the N and 15N excretion of 4-weeks-old male broilers fed 15N labelled wheat. The broilers excreted an average of 1143 mg N per bird per day. This would correspond to a level of N retention of 1105 mg N per day (49% of N intake) for birds consuming 2248 mg N daily. 53.9 mg of the 148 mg of 15N ingested on the first day of tracer administration (=36% of the amount administered) were excreted on the same day. Separation of the excreta by chemical means was not found to be a suitable method for the subsequent 15N isotope analysis of faecal and urinary N. Only colostomated birds can be used if the degree of labelling of faecal and urinary N has to be determined.