Abstract. Antimicrobial sensitivity tests were performed on four-hundred and ninety-seven bacterial isolates from Sudanese patients with diarrhea or urinary tract infections. Shigella dysenteriae type 1 and enteropathogenic Escherichia coli showed high resistance rates (percentage of isolates showing antibiotic resistance) against the commonlyused antimicrobial agents: ampicillin, amoxicillin, chloramphenicol, tetracycline, cotrimoxazole, nalidixic acid, sulfonamide, and neomycin, and were completely sensitive to ciprofloxacin. Eighteen resistance patterns against nine antimicrobial agents tested were observed in enteric pathogens. Resistance to ampicillin, amoxicillin, tetracycline, cotrimoxazole, and sulfonamide was the most frequent pattern. The common urinary pathogens, E. coli, Klebsiella pneumoniae, and Proteus mirabilis showed high rates of resistance to ampicillin, amoxicillin, cotrimoxazole, tetracycline, sulfonamide, trimethoprim, streptomycin, and carbenicillin. We recommend that physicians seek updated knowledge of the common antibiotic-sensitivity patterns when starting empirical antibiotic therapy in Sudanese patients with diarrhea or urinary tract infection.