97 strains of Escherichia coli (49 from urine and 48 from non-urine sources) were isolated from patients at Children's Memorial Hospital, Oklahoma City, and studied for antimicrobial susceptibility. The proportion of highly resistant strains (growth at a concentration of 50 microgram/ml or more) was 27% with ampicillin, 25% with tetracycline, 23% with cephalothin, 6% with kanamycin and neomycin, 4% with chloramphenicol, and zero with colistin, gentamicin, and tobramycin. 23 strains (24%) were found resistant to two or more antibiotics simultaneously. The incidence of strains resistant to ampicillin, cephalothin, kanamycin, neomycin, and tetracycline was higher among urine isolates than among non-urine isolates.