The occurrence of the endocrine disruptor compounds, such as 4-nonylphenol isomers and bisphenol A was determined in surface water samples from Portugal. The analytical method used involved the preconcentration of 200 mL of water sample by solid phase extraction (SPE) using a OASIS (Waters) cartridge, followed by Gas Chromatography-Mass Spectrometry (GC/MS) determination. Recoveries and limits of detection of 4-nonylphenol isomers and bisphenol-A were 73 % and 119 %, respectively, 0.01 mg L-1 and 0.002 mg L-1. The method was applied to the determination of these estrogenic pollutants in river and coastal waters during three months (August-October/1999). The total samples analyzed were 135. Concentrations of 4-nonylphenol isomers and bisphenol-A ranged from 0.03-30 mg L-1 and 0.07-4.0 mg L-1, respectively. Only in two river samples, concentrations of 4-nonylphenol isomers were above 10 mg L-1 and bisphenol-A were above 2 mg L-1. These values can cause estrogenic effects in fish and these sampling points require further investigation in order to verify the maintenance of these levels.D. A. A. acknowledges a grant from CNPq. Direção Geral do Ambiente, Ministério do Ambiente (Portugal), the EU project of the waste water cluster SANDRINE (ENV4-CT98-0801) and CICYT (AMB/999-1705-CE) are acknowledged for financial support to this project. Rosa Alonso and Roser Chaler are acknowledged for technical assistance.Peer reviewed