The relationship between changes in tissue lipoprotein lipase (LPL) activity and triglyceride (TG) concentration has been studied in chronically uremic rats. Uremic rats had a 6-fold increase in BUN and 75% rise in TG levels associated with a 50% reduction in adipose tissue heparin-releasable LPL activity. However, total LPL activity of adipose tissue and muscle was not significantly decreased. Furthermore, there was no significant correlation between the rise in plasma TG concentration seen in uremic rats and the reduction in heparin-releasable adipose tissue LPL activity. These data suggest that the TG removal defect associated with chronic uremia is not a simple function of a decrease in LPL activity.