Previously healthy infants younger than 2 months of age without evidence of soft tissue or musculoskeletal infection who had white blood cell counts between 5000 and 15,000/mm3, band form counts less than or equal to 1500/mm3, urinalysis less than or equal to 10 white blood cells/high power field (spun sediment) and stool less than or equal to 5 white blood cells/high power field (if diarrhea) were considered at low risk for a serious bacterial infection. Infants meeting these criteria whose parents were judged to be adequate observers and had a telephone and automobile were eligible for outpatient management. Infants were given ceftriaxone to cover the possibility that the low risk criteria might miss more infants with serious bacterial infections than was predicted. From Jan. 1, 1987 to May 31, 1989, 86 infants younger than 2 months were enrolled. There were no serious complications in these infants. Twelve had transient problems possibly related to the intramuscular ceftriaxone therapy. One low risk infant was hospitalized for Neisseria meningitidis bacteremia and five other infants were hospitalized for medical or social reasons. All six hospitalized infants had short admissions and did well. This study supports the continued use of the low risk criteria to distinguish infants unlikely to have a serious bacterial infection. Furthermore, in a selected group of low risk infants, outpatient management may be an acceptable alternative to inpatient therapy.