The direct effects of D(2-ethylhexyl)phthalate (DEHP), on subcutaneous tissue were studied in the rat, using the air pouch technique. Two ml of DEHP either undiluted or diluted in olive oil (10 microm/ml), were introduced into a previously created air pouch in the rats. The air pouch was removed and specimens of the lining tissue examined by optical and electron microscopy. The persistence of DEHP for 7 days is sufficient to cause alterations in the tissue. The major histological changes were the destruction of the tissue organization with cytoplasmic and nuclear alterations resulting in apoptotic bodies. The histochemical data showed an increase of sulphated glycosaminoglycans, showing proof of alterations in fibroblast functions. The authors suggest that the hyperplastic-type alteration induced by DEHP may be connected with the sclerosis of the peritoneal membrane described in uremic patients in CAPD.