To develop a technique for quantitative analysis of resting thallium scintigrams, an understanding of thallium kinetics at rest is required. This study evaluates in normal man the thallium distribution and washout rates of thallium at rest and compares these findings to similar data obtained during exercise. The thallium half-life in normal resting myocardium is significantly longer than after exercise, 10.2 +/- 1.4 hours versus 3.9 +/- 0.3 hours (P less than .01). Differences in resting thallium half-life exist between the anterior, 45 degrees left anterior oblique (LAO), and 70 degrees LAO views and are 11.4 +/- 1.0, 10.6 +/- 1.0, 8.8 +/- 0.7 hours, respectively (all significantly different from each other by ANOVA, P less than or equal to .01); these differences are related to the imaging sequence. After exercise, the thallium half-life also varies according to imaging sequence, but in the opposite direction; i.e., anterior, 45 degrees LAO, and 70 degrees LAO views are 3.6 +/- 0.1, 3.9 +/- 0.3, 4.2 +/- 0.3 hours, respectively (P less than or equal to .01). Since imaging sequence and time of acquisition at rest and exercise were similar, this finding may be related to earlier maximal uptake of thallium after exercise as compared to rest. There are also significant segmental differences in thallium half-life at rest in the 45 degrees LAO view (9.8 +/- 0.9, septal vs. 11.0 +/- 0.9, posterolateral, P less than .01) and 70 degrees LAO view (8.3 +/- 0.4, anteroseptal vs. 9.2 +/- 0.6, inferior, P less than or equal to .01).(ABSTRACT TRUNCATED AT 250 WORDS)