Smoking-related cues tend to produce urges and cardiac responses in smokers. This reactivity has been assumed to reflect prior classical conditioning. However, little direct evidence exists supporting the notion that environmental cues can be classically conditioned to cigarette smoking. In this study, 8 smokers received 22 daily trials during which 2 cue complexes (comprising visual, olfactory, and auditory stimuli) were paired with smoking (CS+ trials) and not smoking (CS- trials). Reactivity to the environmental cues, as measured by self-report of urge and pulse rate, increased across CS+ trials, diverging from responses in the CS- trials. Reactivity was stronger among light smokers and those who verbalized awareness of smoking contingencies. Findings indicate that environmental cues can be classically conditioned to smoking.