Among 87 strains of Vibrio choleare (78 Ogawa serotype and 9 Inaba serotype strains) isolated in Angola in 1987-1990, 86% exhibited multiple resistance to antimicrobials. Eighty-four to 86% of strains were resistant to ampicillin with beta-lactamase production (MIC greater than or equal to 512 mg/l), streptomycin (MIC greater than or equal to 64 mg/l), spectinomycin (MIC greater than or equal to 1,024 mg/l), and trimethoprime-sulfisoxazole (MIC greater than 1,024 mg/l). Seventy-four per cent of strains were resistant to kanamycin (MIC = 512 mg/l), 26% to chloramphenicol (MIC = 32 mg/l), 10% to tetracycline (MIC = 16 mg/l), and 10% to gentamycin (MIC greater than or equal to 32 mg/l). Transfer to E. coli K12 was associated with a substantial increase in expression of resistance to tetracycline and chloramphenicol (CAT type I), with MICs in the 128-512 mg/l range. Transfer rates to E. coli K12 of plasmids for the various resistance phenotypes were 10(-6)/10(-8). The size of the isolated plasmids was 100 Md in diameter and belonged to the incompatibility group inc 6-C.