In experiment I, male and female rats from the spontaneously hypertensive (SHR) and Wistar-Kyoto (WKYN) normotensive strains were given I session of 2-way shuttlebox avoidance training at 25-26, 35-36, or 45-46 days of age. The avoidance training was preceded by a pretest which consisted of 10 presentations of the compound conditional stimulus alone in order to assess any differential tendency of the 2 strains to respond to the presentation of novel stimuli. The WKYN rats made a significantly higher number of pretest avoidance responses and achieved a higher level of avoidance performance than SHR rats. In addition, during the pretest, WKYN rats were more active and had a shorter 1st trial latency. In Experiment II, the pretest phase was replicated with a manipulation of the intensity of the auditory cue. Although the WKYN rats had a higher rate of pretest avoidance than SHR rats, the rate of pretest avoidances increased with intensity in both strains. The WKYN rats had a shorter 1st trial latency and a shorter median latency for the 10 trials and were more active that SHR rats during the pretest. These results relate to age-independent behavioral characteristics of these strains and the question of reactivity to environmental stimulation.