The patients were divided into 3 groups: 127 cases of cor pulmonale, 47 cases of glomerulonephritis and 17 cases of coronary heart disease. Erythrocyte deformability indices (DI) and changes during extracorporeal thrombosis were investigated in all the 3 groups, in comparison with a group of 80 normal healthy individuals. The result showed that all the patients had notably lower DI (respectively 1.21 +/- 0.99, 0.73 +/- 0.93), and 0.84 +/- 0.81 for the groups in the given order), longer length of extracorporeal thrombi (L in mm, respectively 45.94 +/- 38.78, 62.88 +/- 43.65 and 59.74 +/- 40.99) and larger top inclination angle of blood plane in silicon-lined ring tube (respectively 15.66 degrees +/- 6.09 degrees, 13.21 degrees +/- 9.33 degrees and 12.65 degrees +/- 8.02 degrees) than individuals over 40 in the comparison group. In the group of cases of cor pulmonale, patients with abnormal pH and respiratory failure had apparent greater L than those with pH compensation and without respiratory failure; diminished DI were also observed in association with pH abnormality. In the group of nephritis, patients with renal failure and chronic nephritis showed evidently lower DI than those without renal failure but acute nephritis; increased L were also noted in association with renal failure. In addition, a similar comparison was done between individuals over 40 and individuals at or younger than the age of 40. It was found that people over 40 tended to have diminished DI, increased L and Wt of extracorporeal thrombi, and augmented initial inclination angle of blood plane though not as notably as what was observed in the 3 groups of victims of blood stasis.(ABSTRACT TRUNCATED AT 250 WORDS)