as botulism is a common disease in buffaloes raised in the low lands of the state of maranh？o, brazil, the occurrence of clostridium botulinum spores was evaluated in buffalo breeding areas of 4 municipalities in the "baixada maranhense". twenty eight samples of faeces, mud and soil were collected and divided into 140 subsamples, being 40 of faeces, 65 of mud and 35 of soil. botulinum toxin was detected in the filtrates of 104 cultures (74.28%) from 140 subsamples through the inoculation of mice. using the microcomplement fixation technique for the identification of c. botulinum toxins, type c (14.29%), d (82.14%) and cd complex (3.57%) were found. no significant differences (p>0.05%) between faeces, mud and soil samples were observed. there was a high contamination with c. botulinum spores of the buffalo faeces, mud and soil in the areas studied. identification of other types and subtypes of c. botulinum was not attempted.