In 10 subjects of a particular inbred strain of rats (WAG/Rij), two types of spike-wave complexes were detected in the cortical electroencephalogram (EEG) during the two recording hours. The first type, already well-known, occurred in 8 of the 10 rats. This type was seen both during sleep and wakefulness and was accompanied by behavioural concomitants, reminiscent of human petit-mal epilepsy. A mean of 18 discharges/h was found. The second type, a novel one with a differential shape, occurred in 7 rats with a mean number of 14 discharges/h. In contrast to the first one, this spike-wave complex was not accompanied by behavioural correlates and was almost exclusively present during wakefulness. Four reasons make this strain of rats attractive as an additional animal model for epileptogenic activity: the occurrence of two types of spike-wave complexes, the high percentage of animals showing these phenomena, the genetic constitution of these rats and the fact that they are commercially available.