This paper describes an aerial census of the Nelchina herd of Alaska caribou (Rangifer tarandus), located in south-central Alaska. The census was taken February 23-27, 1962, by the method of stratified random sampling. The areas currently utilized by the herd were divided into strata on the basis of population densities, and each stratum was gridded into 4-square-mile sampling units. The number of units allocated for sampling each stratum was proportional to the estimated population therein, thus permitting greater sampling effort in those strata with high caribou densities--a procedure known as optimum allocation. The initial allocation was adjusted so that at least 15 percent of the area in each stratum was sampled. The relation of the strata means and variances was examined to establish a reference which may be used for the allocation of sampling effort in future surveys. The population estimate for the areas sampled by this technique was found to be 54,452 ± 11,867, with 95 percent confidence limits. A direct count was made in a few areas where stratified sampling could not be used. A conservative final population estimate for the Nelchina herd was 71,000 animals.