House lizards are able to regenerate their tails. This is an ideal model to study the growth and differentiation of an organ. Prostaglandins (PGs) are local hormones having diverse and potent biological activities. In an effort to understand PG metabolism during the growth and differentiation of the regenerating lizard tail, we analysed the fatty acid (FA) composition of phospholipids are free FAs by GC, the activity of two rate-limiting enzymes (phospholipases A and C), the activity of the enzyme responsible for the oxygenation of polyunsaturated fatty acids to PGs (cyclooxygenase) and characterized the endogenous PGs by HPLC. It was observed that on the 20th day, i.e. the tissue differentiation period, there was an increase in phospholipase A activity, together with a sudden fall in the free arachidonic acid (AA) level, an increase in cyclooxygenase activity and the appearance of endogenous PGE2. PGE2 can stimulate cyclic adenosine monophosphate (cAMP) production and it may stimulate a cascade of events associated with tissue differentiation.