Five "big ticket" medical technologies (BTTs) in 1990 were compared in the 24 OECD countries in relation to population, the number of physicians, gross domestic product (GDP), and health care expenditures (HCE). Wide variations were observed between and within countries for all measures. Regression analysis revealed that HCE explains part of the variation in the distribution of computed tomography scanners (excluding Japan), magnetic resonance imaging units, and radiation therapy units (R2 between 0.40 and 0.69), but not extracorporeal shock wave lithotripters. To a lesser extent, GDP was also found to correlate with the distribution of these technologies, but no correlation was found with number of physicians. Other factors affecting the diffusion of these technologies are proposed for study.