1. Cigautoxins (CTX) were extracted from flesh and viscera of seven large roving predatory fishes: Caranx bartholomaei, Caranx latus, Seriola dumerili, Alectis crinitus, Scomberomorus cavalla, Sphyraena barracuda and Gymnothorax funebris. 2. Generally each extract consisted of close-related CTX which were separated according to their polarity by Florisil column chromatography into a fast-acting CTX containing group and a slow-acting CTX containing group. 3. The shortest survival time of mice (ts) was low for the former group (less than 10 min) and high for the latter (greater than or equal to 29 min). 4. The level of purity had no influence on the range of ts values. The presence of these two CTX groups in different extracts did not from experimental conditions. 5. Attempts to convert fast-acting CTX to slow-acting CTX and vice-versa were negative. G. funebris and S. barracuda had an especially high content of unstable fast-acting CTX. 6. Purification of the slow-acting CTX was achieved by fast elution chromatography and Sephadex LH20 gel filtration. 7. The ts values of these CTX were identical for five species (40-44 min) but not for S. barracuda (29-32 min). 8. Thus ciguatoxic extracts from Caribbean fish were composed of several close-related CTX.