PURPOSE: To better understand a diagnosis corresponding to mental distress and sleep disturbance associated with seasonal change known as seasonal affective disorder (SAD). DESIGN: This ethnographically guided investigation, conducted from 1993 through 1995 in Tromsøo, Norway at a latitude of 69 degrees north describes how the residents experience extreme seasonal change. METHOD: Qualitative interview data from 28 participants plus observation, folk wisdom, and literature were used to describe local understanding of seasonality and illustrate how cultural values, meanings, and practices can contribute to alternative experiences that differ from scientists' expectations. FINDINGS: While there is evidence that human physiologic alterations occur in response to the changing seasonal patterns of light and dark and to a greater extent, at latitudes further from the equator, the findings related to psychological changes and their causes remain inconsistent and controversial. CONCLUSION: Investigators concerned with the effects of seasonal change should be aware of and develop an appreciation of cultural perception and adaptation.