The effect of a ten-day caloric restriction period and of subsequent refeeding on adipose tissue lipoprotein lipase (LPL) activity was studied in 14 moderately obese women. The enzyme assays were made from subcutaneous fat taken from three separate regions (gluteal, femoral, and abdominal) after overnight fasting and from one region also after a standard meal. There was a close correlation between the activities measured from the different subcutaneous sites. The caloric restriction was followed by a decrease of the basal LPL activity to one fifth of the value recorded during the isocaloric diet. However, the relative postprandial increase of LPL activity was greater during the low-calorie diet than during the isocaloric diet. During refeeding the basal LPL activity rose but remained at a lower level than before the caloric restriction. The postprandial LPL response was markedly exaggerated after ten days of refeeding (21% increase before dieting and 250% after refeeding). The changes of LPL during caloric restriction and subsequent refeeding were not correlated to plasma insulin levels. The mechanism of the exaggerated LPL response to meal during refeeding remains obscure.