Calcium "uptake" was measured in vitro in rat epididymal adipose tissue. Lipolytic agents such as catecholamines (1-noradrenaline and 1-isopropylnoradrenaline) synthetic alfa1-24 ACTH and theophylline enhanced the calcium "uptake". Insulin, prostaglandine E1 and nicotinic acid significantly inhibited lipolysis as well as calcium "uptake". Experimental evidence is presented indicating, that calcium "uptake" in sections of rat adipose tissue may be regulated by the tissue free fatty acid concentration.