We have previously described the syndrome of winter seasonal affective disorder (SAD). SAD is characterized by symptoms of depression that recur regularly during the fall and winter and remit in spring and summer. Although the clinical picture of SAD has been well delineated, little research has been done on its longitudinal course. In this report we complete the description of the follow-up study findings described in last year's report. Although SAD has been described primarily in adults, we and others have reported on a small number of children and adolescents with the syndrome. We expanded our knowledge by studying epidemiological and clinical features of SAD in children and adolescents. SAD has been recognized as a syndrome predominant in females (4 out of 5). However, systematic studies to date have not examined differences in gender with respect to clinical presentations or response to light therapy. We report on the gender difference findings for SAD patients collected over the years. A study of 59 adult patients, discharged from our clinic over 7 years ago indicated that 25 (42%) remained """"""""exclusively seasonal."""""""" Those who experienced other, non-seasonal pathology endorsed substantial degrees of seasonality and continue to demonstrate seasonal patterns of symptoms. Twenty-four of the 54 (44%) patients who initially used light treatment continued to use light therapy regularly and successfully each winter to the present. 1,835 Elementary and middle school students of montgomery County were given questionnaires assessing seasonality. Overall, 3% reported clinically significant difficulties. For grades 6 through 9 the prevalence averaged less than 2% for grades 10 through 12 it averaged over 5%. Given previous adult estimates in Montgomery County at approximately 6%, it appears that seasonality problems fulminate around 15 years of age. Females represented 55% of cases and males 45%. In addition, the distribution of prevalence appeared different for females and males such that female prevalence increased with puberty and male prevalence was split between prepubertal and postpubertal groups. A multivariate analysis indicated that a decline in grades and feeling worst and most irritable in the winter months best discriminated between SAD cases and non-cases. In girls eating also contributed to discriminating SAD cases from non-cases. A linear discriminant function analysis revealed that four variables best differentiated women from men. These were carbohydrate craving, winter sleep length, percent seasonal weight change (all greater in women), and severity of seasonal change (greater in men). 93% of women but only 28% of men were correctly classified regarding gender, suggesting that women with SAD are a more homogeneous group than men with SAD. No gender differences with regard to light response were detected.