Plasma elastase is considered to indicate neutrophil elastase that has been released in vivo and has complexed with plasma inhibitors. Because smoking may play a pathogenetic role in emphysema by inducing elastase release in the lung, which may be reflected in the plasma elastase level, we evaluated the effect of smoking on plasma elastase in healthy men by using an enzyme-linked immunosorbent assay. No significant difference was found in plasma elastase levels between 30 smokers and 29 nonsmokers (103 +/- 23 [SD] ng/ml vs. 97 +/- 23 ng/ml). We found no significant change in plasma elastase level in eight heavy smokers when we compared morning with afternoon plasma samples taken about 7 hours later, while the subjects continued to smoke ad libitum in the interval. However, we found a significant rise in plasma elastase level in 12 healthy smokers who were tested after 8 hours of abstinence from smoking and then immediately and 1/2, 1, and 2 hours after intense smoking (eight cigarettes smoked over a period of 2 hours). Neutrophil count increased from a baseline of 3.8 +/- 0.7 X 10(3)/mm3 to 8.0 +/- 2.5 X 10(3)/mm3 at 1 hour, and 8.8 +/- 3.1 X 10(3)/mm3 at 2 hours. Plasma elastase level increased significantly (P less than 0.02) from a baseline of 111 +/- 30 ng/ml to 141 +/- 24 ng/ml at 1 hour after completion of smoking, but was not significantly different from baseline 2 hours after smoking (130 +/- 34 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)