1. The bile acids composition of the harp seal, Phoca groenlandica, collected around Newfoundland, Canada, had been examined. 2. 13C n.m.r. spectroscopy of the crude bile extract was superior to t.l.c. analysis in revealing the presence of phocaecholic acid and a taurine moiety in this mixture. 3. The relative percentage of cholic, phocaecholic and chenodeoxycholic acids was 60.5% (+/- 4.5), 21.4% (+/- 4.0) and 18.1% (+/- 5.8), respectively. 4. The variation in the percentage of bile acids did not correlate with the sex of the sampled animals, but varied significantly with the age of the seals.