The need to have methods as alternatives to animal bioassays for marine-toxin detection is of paramount importance. Such methods require not only identification of each of the analogs in a phycotoxin group but also the toxicity of each analog. Depending on the nature of the method, not all that have been proposed as potential replacements are equally suitable for the task. The evidence suggests that physico-chemical methods are by far the most prone to generating larger errors. Antibody-based methods in many cases exhibit the same difficulties, whilst receptor-based methods have been developed to measure the concentrations of toxin present in samples based on the relative toxicity of all analogs. This review identifies the advantages and the disadvantages of each type of method, with particular emphasis on toxicity identification.