Aims: Two different screening methods, a Buffalo Green Monkey cytotoxicity test and a biosensor test, have been considered to replace the official mouse bioassay in monitoring for okadaic acid (OA) levels in mussels. Methods and Results: Diarrhoetic shellfish poison-contaminated mussels from the Adriatic Sea were assayed in parallel by means of the mouse bioassay and both alternative methods. Both the cytotoxicity test and the biosensor test showed high sensitivity (OA 0.01 mg g(-1) hepatopancreas and 0.002 mg g(-1) hepatopancreas, respectively) and a high correlation with the mouse bioassay (r = 0.932, P < 0.001 and r = - 0.850, P < 0.001, respectively). Conclusions: Both methods are efficacious, quick, inexpensive and provide data on the amount of toxin present in mussels. Significance and Impact of the Study: Both methods, besides allowing the simultaneous assay of a great number of samples, comply with the ethical need to reduce the use of animals in the laboratory.