Nematodes of the genus Anisakis have marine fishes as intermediate hosts. One of these hosts is Thyrsites aeon, an important fishery resource in Chile between 38 and 41 degrees S. This paper describes the frequency and number of Anisakis nematodes in the internal organs of Thyrsites atun. An analysis based on spatial distribution models showed that the parasites tend to be clustered. The variation in the number of parasites per host could be described by the negative binomial distribution. The maximum observed number of parasites was nine parasites per host. The environmental and zoonotic aspects of the study are also discussed.