An association of septic thrombophlebitis with acute osteomyelitis in four children is described. Each patient presented with physical findings consistent with thrombophlebitis. Venography, done in two, demonstrated significant acute thrombophlebitis, and another had an infected venous cutdown. A subperiosteal abscess was the predominant bony involvement found in all three patients who underwent surgical drainage. The initial radiographs were normal in each case. Bone scans showed diffuse increase in activity in the extremity, consistent with hyperemia, but no focal areas of increased uptake to suggest osteomyelitis. Computerized tomography, done in two patients, failed to reveal any bony abnormality, although subperiosteal abscesses were drained within 48 hours of each study. The existence of reverse collateral venous flow through the bone, associated with a rise in intramedullary pressure, may be responsible for these findings.