Two female Hemiechinus auritus syriacus (litter mates) were kept together for 4 weeks and demonstrated intense homosexual activity and prolonged oestrus during the entire period. This resulted also in an unwillingness to mate for one and a half, and two and a half years, respectively. A comparison of this abnormal behaviour and its results, with the different sexual effects described in laboratory rodents and domestic animals, indicated that these wellknown effects cannot be demonstrated in Erinaceinae, the effect of the stimuli being mostly quite contrary.