Growth rate is a prognostic factor for pulmonary metastases treatment. We used computed tomography (CT) to quantify tumor doubling time (Tdt) variation of pulmonary metastases in the same patient, from different histologies and sizes. We prospectively evaluated chest CTs of patients with pulmonary metastases under no cancer treatment. Tdt of 408 pulmonary nodules in 21 patients was determined. One hundred twenty-three (30%) remained unaltered, 44 (11%) had reduction, and 241 (59%) increased in size. Nodules that grew presented a mean Tdt of 118 +/- 134 days (range: 22-930 days). There was high intraindividual variability of mean Tdt with no difference between histologies. Smaller nodules presented greater tendency to grow, and lower Tdt. There is large variation in clinical behavior for pulmonary metastases in the same patient. Each nodule should be evaluated independently. Selection of a single nodule to evaluate metastatic disease behavior could influence the therapeutic decision.