The five castes in Brave New World are named after the first five letters in the Greek alphabet. They are Alpha, Beta, Gamma, Delta, and Epsilon. The Alphas are the most intelligent caste, and the intelligence level descends moving through the castes, with Epsilons being the least intelligent. Within the castes, too, there are three levels. One, for example, can be a Beta plus, a Beta, or a Beta minus.

People within a caste are conditioned from birth to be comfortable in their caste. This is done through repeatedly being subjected to hearing the same tapes while asleep. Betas, for example, are taught thousands of times that the khaki color Deltas wear is hideous and to be glad that are not Deltas. Harsher methods are also used to condition children. Deltas, for instance, who will largely live in urban areas and do rote factory work, are conditioned with loud noises and electric shocks to loath and fear books and flowers while they are still babies.

The gender and race of the caste reflects the sexism and racism of the time period. The Alphas in the novel, for example, are, on the whole, tall white males, reflecting the idea that white men are the most intelligent group and should be in charge. All the Betas, who are the less intelligent consumers, are women. As the castes descend, they get smaller in size and more Asian or Black in features and skin tone, reflecting 1920s and early 30s stereotypes.