The objective of this study was to determine the presence of metazoan parasites and epibionts in the pleasure oyster Crassostrea corteziensis (Hertlein) inhabiting two coastal and fishing localities in the Mexican Pacific state of Sinaloa. 30 oysters were collected in the fishing cooperative of Playa Norte in the bay of Mazatlán, Sinaloa and a comparison made with the presence of parasites in oysters in the "Ceuta"coastal lagoon. Inspection of oysters in the coastal lagoon revealed the presence of 36 encapsulated metacercariae of the Acanthocolpidae family in the gonad of the oyster Crassostrea corteziensis. Six metacercariae were found in the Mazatlán bay Playa Norte area: three of sp. 1 (Family Hemiuridae) in the mantle, a specimen of sp. 2 (Family Fellodistomidae) in the digestive gland and a metacercaria sp3. unidentified in the mantle and a metacercaria (Family Zoogonidae) in the ...