Hafnia alvei is a gram-negative bacterium that is rarely isolated from human specimens and is rarely considered to be pathogenic. It has been associated with gastroenteritis, meningitis, bacteremia, pneumonia, nosocomial wound infections, endophthalmitis, and a buttock abscess. We studied 80 H. alvei isolates recovered from 61 patients within a period of 30 months. H. alvei was cultured from sites that included the respiratory tract (n = 38), the gastrointestinal tract (n = 16), and the urogenital tract (n = 12); the organism was found in blood cultures (n = 8), on central venous catheters (n = 3), and on the skin (n = 3). Only 25% of H. alvei isolates were recovered in pure cultures. Fifty-seven (93.4%) of the patients had an underlying illness. H. alvei proved to be the etiologic agent in two episodes of septicemia and in one episode of peritonitis and was probably responsible for septicemia in two other patients and pneumonia in one. All six of these patients recovered after receiving antibiotic treatment and/or standard surgical treatment, when needed. Three of these infections were nosocomial, and three were community acquired. Of the strains of H. alvei tested in our study, 100% were susceptible to netilmicin, ciprofloxacin, and imipenem; 92% were susceptible to piperacillin; 90% were susceptible to co-trimoxazole; and 88% were susceptible to ceftriaxone and ceftazidime. In this study, we found H. alvei to be a rare significant etiologic agent of nosocomial and community-acquired infections.