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The breeding of the Black Petrel (Procellaria parkinsoni) on Little Barrier Island was studied during 1971-75 in 22 study burrows and then reviewed at about 2-yearly intervals. Predation by feral cats affected the population most, causing the number of breeding and non-breeding birds associated with study burrows to decline from 39 in 1971-72 to 14 in 1976-77. Cats were eliminated between 1977 and 1980. By 1982-83 further attrition due to poor recruitment had stopped. The breeding season of the Black Petrel is from October to July. Eggs are laid from about 10 November to about 20 January but mainly in early December. Pre-laying activities are brief, but other phases of the breeding cycle are not. Incubation shifts and the nestling period may be long because of limitations of the food supply. The major breeding place is Great Barrier Island. Surveys there during chick-rearing in 1977 and 1978 revealed very little predation and relatively high breeding success. The cause of this is discussed.