AbstractCroton zehntneri is a popular plant used in the Brazilian folk medicine. Recently, the use of its essential oil showed depressive activity on the central nervous system (CNS). Chemical studies show that estragole (ES) is one of the main compounds of this oil. This work seeks to evaluate the activity of ES on behaviour models of depression and anxiety, in rats. Male rats (60 days) were distributed to four groups (n = 10) and treated with 1.0, 3.0 and 10.0 µL/100 g body weight, v.o. of ES (experimental) and saline (control). Forced swimming and open‐field parameters were unaffected by the ES treatment suggesting no alterations on depression behaviour. A decrease was observed in the total time of social interaction in the 10.0 µL/100 g group in relation to other groups. This group showed a reduction in the total entries frequency on the elevated plus‐maze without differences to the other parameters of this test. No differences in holeboard parameters were observed suggesting no alterations in exploratory activity. These data suggest that administration of ES induced alterations in the CNS related to anxiety behaviour, expressed by the shortest total time in the social interaction model. Exposure to ES was capable of altering the motor activity in the plus‐maze test. These data are antagonistic to those observed with the Croton zehntneri essential oil in these models. Copyright © 2004 John Wiley & Sons, Ltd.