The life cycle of Ixodes (Ixodes) loricatus Neumann, reared in the laboratory, is described. Engorged females collected from opossums trapped in the states of Minas Gerais and São Paulo, Brazil, which were used to start the laboratory colonies, were designated as BMG and CSP, respectively. Larval and nymphal ticks from both colonies fed separately on Rattus norvergicus Berkenhout or Calomys callosus Rengger, whereas Didelphis marsupialis L and Didelphis albiventris Lund were used as hosts for BMG and CSP adults, respectively. Biological and developmental data obtained from ticks of both the BMG and CSP colonies that were reared separately for two consecutive generations were compared. The percentage of fed or molted ticks reared on C. callosus was higher than that recorded for ticks fed on R. norvergicus in the majority of the observations. Despite significant differences among several of the biological parameters, the pattern of the life cycles of the two tick colonies was similar. Results indicated that the mean life cycle duration of I. (I.) loricatus was ≈7 mo from parental oviposition to the occurrence of F₁ eggs, regardless of geographic origin or host species.