The aim of this study was to investigate whether there are sex pheromones in the tropical horse tick, Anocentor nitens (Neumann). When virgin males and females, fed on rabbits for 3-7 d, were tested reciprocally, there was a direct correlation between attractiveness and the period of feeding; attraction was greater (and with the fastest responses) in males and females fed for at least 6 d (sexually active males and confirmed attractive females). The capacity of sexually active males to orient topward confirmed attractive females decreased as the emission distance increased; the maximum distance that evoked a response by males was 6 cm. Confirmed attractive females lost their attractiveness approximately 2 h after being separated from the host, or after being killed by ethanol injection, although some females continued to attract sexually active males up to 4 h after death. An extract was produced by immersing confirmed attractive females in hexane and submitting them to ultrasound. Sexually active males were more attracted to and spent more time on glass bead dummies treated with this extract when compared with those treated with the hexane alone. Our results indicate the presence of at least 2 sex pheromones (attractant and mounting) in attractive females of A. nitens.