VISITS to Campbell Island (520 33' S, 1690 09' E) from 8 to 26 January 1969 and to Antipodes Island (490 40' S, 1780 50' E) from 28 January to 12 March 1969 permit some comparisons between two breeding populations of the Rockhopper Penguin (Eudyptes chrysocome) and supplement data gathered at Macquarie Island between 1959 and 1961 (Warham, 1963). The present paper forms part of a series to deal with aspects of the breeding biology of all the Eudyptes penguins. Bailey and Sorensen (1962) describe the distribution and breeding of the Rockhopper Penguin at Campbell Island, which supports many more Rockhoppers than other penguin species. Small numbers of Erectcrested Penguins (E. sclateri) also nest there, and Royal Penguins (E. chrysolophus schlegeli) are not rare though not known to breed. The Yellow-eyed Penguin (Megadyptes antipodes) is the most plentiful penguin after the Rockhopper, but breeds among thick vegetation well away from the latter bird. At Antipodes Island Rockhoppers share breeding beaches and coastal slopes with large numbers of E. sciateri. The latter generally occupy the lower and reasonably flat ground above high water while the Rockhoppers nest higher up, often on steep slopes or within shallow caves. At this island the two species appear to occupy nesting niches equivalent to those Royals and Rockhoppers take up at Macquarie Island where, when the two species are contiguous, the latter again lay higher up among talus debris consolidated by soil, or among tussock grasses. At Campbell Island the data were collected from live birds at a small colony in Rocky Bay below Mt. Dumas and at a larger one at Penguin Bay. At Antipodes Island Rockhoppers occur mainly on the east and south coasts; the data here were gathered at two colonies in the vicinity of the expedition base at Reef Point on the eastern side of the island. Colony locations with indications of size are being mapped and will appear with a general account of Antipodes Island birds (Warham and Bell, MS.). The Expedition was assisted by a grant from the Trans-Antarctic Expedition Research Fund and thanks are also due to the Royal New Zealand Navy for providing transport, to R. Stanley for help in the field, and to K. W. Duncan for advice on statistics.