Six patients with proven or suspected osteomyelitis were studied with both 99mTc-HMPAO-labelled leukocytes and 99mTc-nanocolloid. In all cases the findings of both procedures were in good agreement. In 3 patients there was markedly increased accumulation of labelled cells and colloid, respectively. Two patients showed slightly increased accumulation of both agents and in one patient the finding was (correctly) negative. Further studies are necessary to determine whether or not colloid scintigraphy might replace the time-consuming leukocyte scintigraphy.