In an open study, we determined whether there were sex differences in the mood ratings of non-deprived light smokers and nonsmokers under baseline conditions and after completing a battery of cognitive tests that were mildly stressful. Male and female students who were light smokers (5-12 cigarettes a day) were tested immediately after smoking their usual cigarette, at a time that they normally smoked. They were compared with a group of male and female students who were nonsmokers and did not differ on age, IQ, personality measures, anxiety or depression. Compared with the nonsmokers, both male and female smokers felt overall significantly more discontented, troubled, tense, quarrelsome, furious, impatient, hostile, annoyed and disgusted and experienced greater dizziness. The performance of distracting cognitive tasks did not reveal anxiolytic effects of smoking, and after performance of these tasks, both smokers and nonsmokers became more discontented and anxious. In addition, after the cognitive testing, both male and female smokers showed greater increases than nonsmokers in feeling spiteful, rebellious, incompetent and in sweating, suggesting that they experienced greater mood changes in response to cognitive stress. There were no overall differences between the smokers and nonsmokers in the performance of divided or sustained attention tasks or in episodic memory. It is unlikely that either nicotine withdrawal or differences in cognitive performance could account for the greater anxiety, discontent and aggressive mood that was found in smokers.