The polymicrobial aetiology of travellers's diarrhoea in 356 tourists travelling in Thailand and Burma was investigated. Besides enterotoxigenic E. coli, Salmonella sp. and Campylobacter fetus ssp. jejuni were identified as the most important enteric pathogens. Minimal inhibitory concentrations of several commonly used antibiotics were determined to reveal the percentage of enteric pathogens being resistant. 36.2% E. coli strains were found to be resistant to ampicillin and 14.3% of the Campylobacter isolates were considered to be resistant to erythromycin. Furthermore, the occurrence of some plasmid-borne beta-lactamases causing resistance to beta-lactam antibiotics was investigated, and the TEM-1 enzyme was found to be the most common one in enteric pathogens. Also a PSE-2-beta-lactamase (which is said to be Pseudomonas-specific) was identified in two strains of E. coli. Finally, the influence of antibiotic misuse on development of resistance was discussed by comparing the conditions in Bangkok and Rangoon.