Minimal inhibitory concentration (MIC) determinations were carried out with seven growth-enhancing antibiotics against 95 Clostridium perfringens field isolates obtained during 1991 and 1992 from poultry, pigs and calves. All were resistant to 64 micrograms ml-1 of the bambermycin antibiotic, flavomycin (flavophospholipol) and susceptible to avoparcin (MIC90 0.25 micrograms ml-1), avilamycin (MIC90 0.5 micrograms ml-1) and salinomycin (MIC90 < or = 0.12 micrograms ml-1). Acquired resistance against bacitracin was detected in some isolates from poultry and bovines and resistance to tylosin and virginiamycin in some strains from all species investigated. Overall, the prevalence of resistance was comparable to the low levels recorded in 1979 in Cl. perfringens isolates from the same animal host species.