A study on the breeding biology and diet of Pintado Petrels Daption capense was conducted at Nyrøysa, Bouvetøya, South Atlantic, from December 1996 to February 1997. Overall breeding success for the total 300 pairs of breeding Pintado Petrels at Nyrøysa was 59 %. Three study colonies were marked out and monitored intensively; in one colony overall breeding success was only 4 % owing to predation by Sub-Antarctic Skuas Catharacta antarctica on unattended chicks, but in another colony success was 85 %. Rates of failure were higher during the chick stage than in the egg stage for both of these two study colonies. The mean hatching date in these colonies was 11 January, and the first and last hatching 6 and 18 January respectively. The mean period for which chicks were permanently attended by parents (guard period) was 14 days. The length of the guard period was negatively related to the date of hatching (expressed as the number of days passed since the first egg had hatched i.e. 6 January). Growth of chicks in the third study colony was similar to that recorded for other populations of Pintado Petrel, as was the diet of chick-rearing adults - dominated by euphasiids, especially krill Euphausia superba. Whole female krill occurred more frequently than male krill in the diets of chick-rearing Pintado Petrels at Nyrøysa, and were larger. It is estimated that during the nestling stage the entire Bouvet0ya population of Pintado Petrel chicks consumes 6 500kg krill.