Rats aged between 13 and 18 days were dropped from different heights in order to establish the height at which 50% of the animals were able to perform complete air righting. The proportion of animals showing complete air righting abruptly increased at 16 days of age indicating maturation of the response at this age. No necessary relationship was observed between eye opening and air righting. At 15 days of age, when normally only a minority of the rats are able to display complete air righting, a marked effect of training was observed.