Reproduction of koalas was studied at Lone Pine Koala Sanctuary, Brisbane, where 80% of births fall between October and January. Gestation ranges from 34 to 36 days. Females are monotocous. Those who wean their young in the first half of the breeding season breed again in the second half. Although polyoestrous, most females conceive at their first oestrus, except 2-y-olds. Males are mature at 3 y old, females at 2 y old. Young emerge from the pouch at 7 months, leave it completely at 9 months, and are weaned at approximately 12 months. Growth curves are provided. Those born early in the season grow faster than those born later; the age when growth ceases is unknown. Longevity is about 12y; and the sex ratio may be slightly biased towards females.