The sex ratio and body sizes per sex in populations of intertidal porcellanid crabs vary by species and are related to specific gene expressions, the molecular mechanisms underlying which are still largely unknown (Kasimatis et al., 2021). Typically, porcellanid crabs exhibit sexual dimorphism, where males and females may have different sizes and physical characteristics. This can be influenced by factors such as habitat, food availability, and reproductive behaviours. Detailed studies of specific species and populations are necessary to provide accurate and comprehensive information about the size distributions and sex ratios of intertidal porcellanid crabs. In the present study, we describe size distributions and sex ratios of some intertidal porcellanid crabs, Petrolisthes violaceus, Petrolisthes granulosus, Petrolisthes tuberculatus and Allopetrolisthes punctatus, collected from northern Chile, as well as the probability of sexual maturity of females at a given size (0.66 mm). The results within species for P. granulosus and P. violaceus did not show significant differences in sex ratio, whereas for sex-size structure these two species displayed significant differences. Similar results were observed in populations of P. tuberculatus and A. punctatus. Ecological and reproductive topics are discussed.