This study was intended to provide information on certain aspects of the population ecology of H. pacificus. A population on Quail Island in Lyttelton Harbour was chosen for intensive study over a period of one year. Some information on the population was already available. derived from a preliminary study in 1970 (McIvor, 1970a). The following aspects were investigated; population density, natality and mortality, age structures and sex ratios, annual and seasonal growth, daily and seasonal activity, reproduction (detailed investigation of testicular activity), home range and movements and diet. Much of the population information was obtained from recapture of marked individuals. This study helps to fill some of the major gaps in our knowledge of the biology of the nocturnal gecko. Hoplodactylus pacificus.