The Hardy–Weinberg law has several important implications for the genetic structure of a population. One implication is that a population cannot evolve if it meets the Hardy–­Weinberg assumptions because evolution consists of change in the allelic frequencies of a population. Therefore, the Hardy–Weinberg law tells us that reproduction alone will not bring about evolution. Other processes—such as mutation, migration, or natural selection—or chance events are required for populations to evolve.

A second important implication is that when a population is in Hardy–Weinberg equilibrium, the genotypic frequencies are determined by the allelic frequencies. The heterozygote frequency never exceeds 0.5 when a population is in Hardy–Weinberg equilibrium. Furthermore, when the frequency of one allele is low, homozygotes for that allele will be rare, and most of the copies of a rare allele will be present in heterozygotes.

A third implication of the Hardy–Weinberg law is that a single generation of random mating produces the equilibrium frequencies of p², 2pq, and q². The fact that genotypes are in Hardy–Weinberg proportions does not prove that the population is free from natural selection, mutation, and migration. It means only that these forces have not acted since the last time random mating took place.