The helminth parasites from more than 300 cetaceans stranded on the coast of England and Wales during the period 1990-1994 were identified, this being the largest organized survey of cetacean parasites yet undertaken. Thirteen species of cetaceans were examined, although the majority were common (harbour) porpoises Phocoena phocoena (n=173) and common dolphins Delphinus delphis (n=101). The parasites found included 11 species of nematode (Anisakis simplex, Pseudalius inflexus, Torynurus convolutus, Stenurus globicephalae, S. minor, Halocercus delphini, H. invaginatus, H. lagenorhynchi, H. taurica, Crassicauda boopis, Crassicauda sp.), five cestodes (Diphyllobothrium polyrugosum, D. stemmacephalum, Phyllobothrium delphini, Monorygma grimaldii, Tetrabothrius sp.), five digeneans (Campula oblonga, Oschmarinella albamarina, O. rochebruni, Lecithodesmus palliatus, Pholeter gastrophilus) and two acanthocephalans (Bolbosoma capitatum, B. physeteris). The results of this survey are tabulated and each helminth species is discussed in terms of its biology and pathogenicity.