The raccoon roundworm, Baylisascaris procyonis, is increasingly recognized as a cause of serious or fatal larva migrans disease in humans and animals. We assessed the potential for infection in three northern California communities by determining the density and distribution of raccoon latrines, where transmission primarily occurs, and the prevalence of eggs at private residences. We collected fecal samples from 215 latrines and found that 44%-53% of the latrines contained B. procyonis eggs and that 16%-32% contained infective eggs. Among the properties surveyed, 28%-49% harbored at least one latrine that was positive for B. procyonis eggs. The latrine densities in these communities were higher than any previously reported. The presence of B. procyonis eggs in raccoon latrines was common, widespread, and closely associated with human habitation. Where raccoon densities are high, education of the public and removal of raccoons may be necessary.