Technetium-99m-sestamibi (Tc-99m-MIBI) imaging is a well-established modality in oncologic investigations. The current study aimed to investigate whether any relationship could be found between Tc-99m-MIBI uptake and local perfusion in malignant bone and soft-tissue tumours. It also aimed to compare Tc-99m-MIBI images with those of technetium-99m-methylene diphosphonate (Tc-99m-MDP) bone scintigraphy with regard to the activity distribution pattern, intensity and lesion extension. The study group included 24 patients with various bone and soft-tissue tumours. Three-phase bone scintigraphy and Tc-99m-MIBI studies were performed within the same week before any surgical and therapeutic intervention. Images were evaluated visually and quantitatively using regions of interest (ROIs) over the lesion and adjacent normal tissue. The Tc-99m-MIBI study was positive with varying degrees of uptake (range, 1.4-5.3). The mean Tc-99m-MIBI uptake and Tc-99m-MDP blood-pool and osseous phase activity ratios were 2.5 +/- 0.5, 2.8 +/- 1.0 and 5.5 +/- 4.0, respectively. The correlation between the Tc-99m-MIBI uptake and blood-pool ratios was 0.70 (P<0.05). While activity distribution patterns were in agreement in Tc-99m-MIBI and blood-pool images in the majority of cases, Tc-99m-MIBI better delineated tumour viability and extension in five cases. In conclusion, Tc-99m-MIBI accumulation shows a reasonable correlation with blood-pool uptake assuming the presence of multifactorial mechanisms in addition to local hyperaemia. Better delineation of tumour outlines and cellular activity seems to be an advantage of Tc-99m-MIBI scintigraphy which may be helpful in the evaluation of musculoskeletal tumours. ((C) 2001 Lippincott Williams & Wilkins).