Background: Moderate alcohol consumption is associated with reduced risk for coronary heart disease. This may due, in part to increased fibrinolysis. Monocytes synthesize fibrinolytic proteins, tissue plasminogen activator (t-PA), urokinase plasminogen activator (u-PA), and their receptors. These studies were carried out to determine the effect of low alcohol on monocyte fibrinolytic activity and PA messenger RNA (mRNA) synthesis. Methods: Peripheral blood monocytes and U937 cells were incubated in absence/presence of low alcohol (0.1%, v/v) for various times (0-1 hr), followed by incubations in the absence of alcohol (0-24 hr) before measurement of fibrinolytic activity and PA mRNA levels (reverse transcriptase polymerase chain reaction). Results: Brief exposure (15 min, 4°C) of U937 cells to low alcohol resulted in an approximately 2- to 3-fold increase (269.0 ± 5.6 fmol/1 × 106 cells versus 656.0 ± 94.0 fmol/1 × 106 cells) in fibrinolytic activity. Preincubation of U937 cells and peripheral blood monocytes in low alcohol (1 hr, 37°C) followed by incubation in the absence of alcohol (24 hr) resulted in a sustained approximately 4- to 5-fold increase (414.0 ± 174.7 vs. 965.33.0 ± 104.8 fmol/1 × 106 cells) and an approximately 3- to 4-fold (20.5 ± 2.14 vs. 74 ± 2.28 fmol/2 × 106 cells, respectively) increase in fibrinolytic activity. Preincubation of monocytes with low alcohol (1 hr, 37°C) followed by incubation in the absence of alcohol (6 hr) resulted in an approximately 5- to 6-fold (0.06 ± 0.02 vs. 0.42 ± 0.02) and an approximately 2- to 3-fold (0.89 ± 0.04 vs. 2.07 ± 0.29) increase in t-PA and u-PA mRNA (reverse transcriptase polymerase chain reaction; PA/glyceraldehyde-3-phosphate dehydrogenase ratio), respectively. Conclusions: These data suggest that low alcohol exerts a rapid, direct, and sustained effect on monocyte fibrinolytic activity, which may be, due in part, to increased monocyte t-PA/u-PA expression. These data provide a feasible molecular mechanism by which alcohol effects on monocyte fibrinolysis may contribute to the cardioprotective benefit associated with moderate alcohol consumption.