Evolution annuelle de la sex-ratio de Rhipicephalus sanguineus (Acarina, Ixodidae) en zone urbaine de l ouest algerien.. - The sex-ratio is studied in an urban population of Rhipicephalus sanguineus. Variations are observed related to season and biological activity of the ticks (resting period, moulting, prenutrition, quest activity, blood meal, digestion, preoviposition). If we consider the obtained global results, the mean number of males and females is equivalent throughout the year (sex-ratio 1: 1). However, we can observe a clear prevalence of males in the population attached on hasts, but an overpopulation of unfed and fed females in the free ticks colony (prenutrition, quest activity, digestion). This distribution is related to the reproduction behavior of the investigated species. During the winter rest, when adults have ali the same activity, the sex-ratio lies near 1.