This study presents chemical, pharmacological and immunological data of marine toxin(s) in the gut and flesh ofMulloidichythys auriflamma(weke). Forty‐four per cent of weke tested gave a negative result with the stick enzyme immunoassay (S‐EIA), while 56% were in the toxic category. Extracts of gut and flesh of the positive S‐EIA samples gave high values of 1193 and 1364 mouse units (MU), respectively. Four fractions of the extracts were obtained by silica gel chromatography (CHCl3;10% MeOH/CHCl3;50% MeOH/CHCl3; and 100% MeOH). The toxic fraction from the gut was in the 50% MeOH/CHCl3eluate. Toxic fractions from the flesh were in the 50% MeOH/CHCl3residue. The 50% MeOH/CHCl3fraction of the gut showed strong inotropic and chronotropic effects with no antagonism by tetrodotoxin (TTX) and verapamil, but a significant blockage of the inotropic response was shown with the adrenergic inhibitors propranolol and phentolamine. The 10% and 50% MeOH/CHCl3fractions of the weke flesh were partially inhibited by TTX and verapamil, unlike the viscera fractions. The butyl alcohol extract of the sand appeared to be similar to that of the viscera in the guinea‐pig atrial response.M. auriflammatoxin(s) is highly toxic in mice and appears to be unlike ciguatoxin isolated from moray eel in the guinea‐pig atrium assay.