Of 137 cases of Escherichia coli bacteremia in adults at a general hospital, 16 (12%) were caused by E. coli K1. The case records of 15 patients with E. coli K1 and 48 patients with other E. coli revealed that the patients with E. coli K1 had an average age of 54, while those with other E. coli had an average age of 61 (P greater than 0.05). There was no significant difference between the profiles of underlying disease in the two groups. No patients with E. coli K1 bacteremia died, while 16 of 48 patients with non-K1 bacteremia died (P =0.006). This difference was statistically significant in those patients with ultimately fatal disease (P = 0.038) but not in those with non-fatal disease (P = 0.16). These findings suggest that E. coli K1 is cleared more easily by adults than are other E. coli.