In four out of seven experiments, prostaglandin-like activity was detected in prevertebral venous blood from the superior cervical ganglion, collected during and after preganglionic nerve stimulation.2. Prostaglandins E(1), E(2), F(2alpha) and a prostaglandin A were identified using solvent partition, column and thin-layer chromatography and bioassay techniques.3. The release of PGF(2alpha) was confirmed by combined gas chromatography-mass spectrometry.