The important contribution of P. Rayer to parasitology (human and animal) had never been studied so far. It includes chiefly a dozen papers published in Archives de Médecine comparée (1842-43), a creation of Rayer. They deal with myxosporidia, helminths (nematodes, trematodes) and ectoparasitic insects. In the same periodical are published important parasitological contributions from germanic authors (J. Müller, G. Simon, A. de Nordmann). Three other papers from Rayer (1838, 1850) are devoted to human parasitic diseases (urinary bilharziosis, wuchereriasis) of which the exact etiology was still ignored. Two unpublished letters from G. Breschet and H. M. Edwards to Rayer dealing with the 1842-43 papers are given here. The contribution of Rayer's disciples to parasitology is then recalled: C. Davaine (the most important), Ch. Robin and J.A. Laboulbène.