Among fishes of importance in the Portuguese diet is the mackerel with a large geographical distribution in the Northern Hemisphere. The authors plan to recover the helminths of this host during the year, for taxonomic, zoogeographic and seasonal variation elements studies of potential importance to Public Health. Only six (7.5%) of the first 80 hosts examined (from January to May 1982) were not parasitized. In this paper we report the presence, by order of their frequency in each taxonomic group, of the following helminths: Kuhnia scombri (Kuhn, 1829) and Grubea cochlear (Diesing, 1858) (class Monogenea); Lecithocladium excisum (Rudolphi, 1819) and Opechona bacillaris (Molin, 1859) (class Digenea); plerocercoids of Lacistorhynchus tenuis (Beneden, 1858), of Scolex pleuronectis (Muller, 1788) and of Echeneibothrium sp. (class Cestoda); Rhadinorhynchus tenuicornis (Linton, 1891) (phylum Acanthocephala); larval forms of Anisakis and Contracaecum as well as larvae of Goezia sp. (class Nematoda).Larval forms of the cestode Echeneibothrium sp. and the nematode Goezia sp. are reported in this host, for the first time.