The influence of angiotensin II (ANG II) on the synthesis of glomerular prostanoids is controversial, possibly because of the different methodologies employed. In order to assess this inter-relationship isolated rat glomeruli were incubated with and without shaking. The use of shaking during incubation significantly increased the amounts of prostanoid synthesized, most probably because of continuous non-specific activation of phospholipase (PLA2) activity. After preincubation in a non-shaking bath, ANG II was added for a second incubation period. A marked increase of prostaglandin (PG) E2, and, to lesser degree, of thromboxane (TX) B2 was noted, with no change on PGF2 alpha synthesis. These results show (a) that preincubation without shaking, by lowering the non-specific activation of the PLA2 activity, may unmask, in vitro, specific peptide stimulation, and (b) that ANG II, stimulating principally PGE2 synthesis, may modify the vasoactive status of the glomerular vasculature.