The mechanisms governing the accumulation of granulocytes in inflammatory lesions are poorly understood. Using a sensitive method of sequential 111In-granulocyte scintigraphy, we recorded the speed of focal 111In-granulocyte accumulation in 70 patients with non-osseous inflammatory and infectious foci, with special reference to the influence exerted by the duration of disease, patient age, body temperature, antibiotic therapy and initial trapping of granulocytes in the lungs. About 50% of the images had turned positive at 30 min after injection. Except for patients with urinary tract infections, the age of the patient did not influence the speed of 111In-granulocyte accumulation; nor did the duration of disease, antibiotic therapy or degree of initial granulocyte hold-up in the lungs. High fever, on the other hand, presumably reflecting an intense inflammatory reaction, was associated with an accelerated focal 111In-granulocyte accumulation, indicating that properties of the inflammatory process per se are major determinants of the speed of accumulation of 111In-labelled granulocytes in inflammatory processes.