Sebum production is thought to play a major role in acne vulgaris in adolescents. Psychological stress may exacerbate acne; however, it is not known whether the perceived association between stress and acne exacerbation is due to increased sebum production. The aims of this study were to determine: (i) if psychological stress in adolescents is associated with increased sebum production; and (ii) if stress is associated with increased acne severity independent of, or in conjunction with, increased sebum production. Ninety-four secondary school students in Singapore (mean age 14.9 years) were enrolled in this prospective cohort study. During a high stress condition (prior to mid-year examinations) and a low stress condition (during the summer holidays), the following were evaluated: (i) self-reported stress level using the Perceived Stress Scale; (ii) sebum level at baseline and at 1 h; and (iii) acne severity. The prevalence of self-reported acne in this study population was high (95% in males and 92% in females). Most subjects had mild to moderate acne. Sebum measurements did not differ significantly between the high stress and low stress conditions. For the study population as a whole, we observed a statistically significant positive correlation (r=0.23, p=0.029) between stress levels and severity of acne papulopustulosa. In adolescents, psychological stress does not appear to affect the quantity of sebum production. The study suggests a significant association between stress and severity of acne papulopustulosa, especially in males. Increased acne severity associated with stress may result from factors other than sebum quantity.