In the current study, we examined physical activity in two population based cohorts of Allegheny County. Pennsylvania, which differed markedly in their socioeconomic status (SES), in order to evaluate the relationship of SES to physical activity patterns. A total of 917 individuals participated in a prevalence survey administered during a home visit in 1981. All of the participants were white. Households were randomly selected. An overall response rate of 84% was achieved. Activity was assessed using the Paffenbarger survey, which included the number of blocks walked, stairs climbed, sports and recreational activities, and hours spent in vigorous, moderate, and light activities. In both high and low SES individuals, activity was inversely associated with age and was higher in males than in females. The relationship of physical activity to SES differed depending on the dimension of activity assessed. Participation in sports was reported more frequently in high status males and females. SES was a significant predictor of walking activity in females, with low status females reporting more walking. The number of hours spent in moderate activities was greater, but the number of hours spent in light activities was lower, in low status males. There was little difference by SES in the composite activity score, average annual kilocalories per week. In summary, our research suggests that SES can impinge differently on separate manifestations of activity, and future research needs to identify how SES affects activity.