The records of 559 consecutive outpatient children with unsuspected bacteremia (467 Streptococcus pneumoniae) were reviewed. When compared with patients receiving oral or parenteral antibiotics, those patients who received no antibiotics at the initial visit were in follow-up: (1) less likely to be improved (32% vs. 86%, P < 0.01); (2) more likely to be febrile (75% vs. 28%, P < 0.01); (3) more likely to be hospitalized (67% vs. 22%, P < 0.01); (4) more likely to have persistent bacteremia (28% vs. 3%, P < 0.01); and (5) more likely to have new focal infections (13% vs. 5%, P < 0.01). Compared with patients receiving parenteral antibiotics at the initial visit, patients receiving oral antibiotics were in follow-up: (1) less likely to be improved (81% vs. 89%, P < 0.05); and (2) more likely to have persistent bacteremia (5% vs. 0%, P < 0.05). There was no statistical difference between patients receiving parenteral or oral therapy in the development of focal infections, although children with new focal infections receiving oral antibiotics more often had persistent or new positive cultures. No patients receiving parenteral antibiotics at the initial visit had positive blood or spinal fluid cultures at the follow-up visit. Analyses of the subgroups with (1) occult bacteremia with all organisms, (2) unsuspected bacteremia S. pneumoniae and (3) occult bacteremia with S. pneumoniae show results similar to those for the entire group.(ABSTRACT TRUNCATED AT 250 WORDS)