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The reproductive biology of red-crowned parakeets (Cyanoramphus novaezelandiae novaezelandiae) was studied on Little Barrier Island (Hauturu) during the 1989/90 and 1990/91 breeding seasons. Nests sited in cavities of pohutukawa (Metrosideros excelsa) and puriri (Vitex lucens) trees accounted for all but 1 nest which was found in a hole in the ground. Breeding activity was recorded from Nov to Mar with peak egg laying in Dec. Mean clutch size was 7.0 eggs (range 4-9). Replacement clutches were rare and only followed the loss of young broods. Female parakeets were entirely responsible for incubation that lasted about 23 days. The nestling period averaged 40.8 days (range 32-49) with about a 30% probability of an egg resulting in a fledgling. The main cause of nestling mortality was starvation. Infestation of nests by mites and predation of nestlings were also occasionally recorded. Post-fledging mortality was high, particularly in the 1st 2 weeks, and was attributed mainly to aerial predators such as morepork (Ninox novaeseelandiae). Aspects of nest and roost site characteristics, brood reduction, mortality, and vulnerability to predation are discussed in relation to the conservation of the species.