ABSTRACTHuman subjects (n = 14) were given a discriminated reaction time task in which the imperative stimulus (IS), a puff of air to the face, was both a signal for a voluntary response and an elicitor of a reflex eyeblink. On one‐half of the trials IS was preceded with a lead time of 100 msec by a stimulus (DS) which both inhibited the reflex blink and served as a signal to refrain from the voluntary response. On one‐half of the trials within each DS‐IS and IS‐alone condition a warning stimulus (WS) led IS by 3000 msec. WS produced a decrease in HR and a faster RT, and WS‐IS trials gave greater reflex amplitudes than IS‐alone trials. Eyeblinks were inhibited by DS and reflex inhibition was more pronounced following the warning stimulus. These data suggest that warning stimuli initiate an attentional process oriented to significant stimuli, thus enhancing both the eliciting and inhibiting functions of these stimuli.