Host recognition behaviours were investigated in the Rhabditid nematode Phasmarhabditis hermaphrodita. Infective juveniles were exposed to mucus samples from mollusc species of varying susceptibility (Arion hortensis agg., Deroceras reticulatum, Tandonia budapestensis, Helix aspersa ,Limax flavus, Limax marginatus). Behavioural responses to the mucus were analysed using video-taped sequences. During contact with the mucus samples, infective juveniles decreased duration and frequency of forward crawling and increased frequency and duration of head thrusting and duration of head waving. Other host recognition behaviours identified included body waving and pushing. Most significant differences in behaviour recorded were between controls and during exposure to mollusc mucus; there were few significant differences between mollusc species. The results suggest that P. hermaphrodita forages by the 'cruise' method until mucus from potential hosts is encountered, but then concentrates its search behaviour, characterised by the decrease in forward crawling. However, there were no recorded behaviours that would differentiate between readily susceptible species and those with low or unknown susceptibility.