Polyether toxins are produced by many species of marine dinoflagellates, comprising approximately a dozen genera. These polyether compounds are responsible for certain human intoxication syndromes linked to seafood consumption (ciguatera, DSP, NSP), and also include "fast-acting toxins" of poorly defined human health significance (e.g., gymnodimine, spirolides). Despite recent advances in structural elucidation, relatively little is known about the structural/functional relationships of these secondary metabolites derived via polyketide biosynthesis. Comparison of toxin profiles among natural dinoflagellate populations typically reveals a high degree of structural polymorphism and geographically distinct patterns. Yet the toxin spectrum is usually preserved upon transfer into clonal culture, and tends to be quite refractory to environmental perturbations - this suggests a strongly defined genetic template. However, the toxin cell quota may vary markedly over the culture cycle in response to physiological changes. The metabolic cascade leading to the synthesis of DSP toxin derivatives by the benthic dinoflagellate, Prorocentrum lima, and spirolide production by the planktonic species, Alexandrium ostenfeldii, has been investigated using photoperiod-induced cell synchronisation techniques. The polyether toxins are constitutively produced - they are not classic "stress" metabolites. Current efforts are focused on establishing the timing and sequence of key cell cycle events involved in the biosynthesis of polyether toxins. Although it is not possible to definitively ascribe a functional role to the polyether toxins, and gene regulation of toxin production remains poorly understood, hypotheses concerning their evolutionary significance and biogeographical distribution must be addressed.