Recently, a point mutation in the coagulation Factor V gene (G to A in position 1691) has been identified which makes the mutant Factor V (called Factor V Leiden) resistant to activated protein C. This defect is a well established genetic risk factor in venous thrombosis. Because of the high prevalence of Factor V Leiden in normal population (2-7%), it would be reasonable to perform a rapid and simple method for screening the genetic abnormality in population at risk. We have developed a simple, reproducible, rapid and cheap procedure that, using PCR and SSCP, allows the identification of the mutation responsible for Factor V Leiden. Specificity of this method has been tested in 319 samples: 304 normal, 14 heterozygous and 1 homozygous for Factor V Leiden. This assay allows non-isotopic Factor V Leiden identification by using frozen whole blood in 3 h. All these features make this test adequate for routine screening of this mutation in a large number of samples.