Two experiments are reported which investigated the effects of pre-shock treatment in rats on adrenocortical activity and susceptibility to later restraint-induced ulceration. In Experiment I, animals were exposed to a single inescapable 3 minute shock on 5 consecutive days. These shocked animals exhibited sensitisation of the adrenocortical response over days, increased adrenocortical reactivity to open field testing one week later and a trend for more severe ulceration after 20 hours of restraint. In Experiment II, animals were given 20 escapable or yoked pre-shock trials on 5 consecutive days. No sensitisation of the adrenocortical response was observed. Escape animals however were found to exhibit less gastric ulceration and a reduced adrenocortical responses after 20 hours of restraint 9 days after the last preshock session.