['To explore the effect of multiple prothrombotic risk factors in individuals with anticardiolipin antibodies (aCL), we evaluated immunologic, coagulation, and genetic prothrombotic abnormalities in a cohort of individuals with different aCL titers.', 'We recruited 87 individuals into 4 categories (normal, low, intermediate, or high) based on their baseline IgG aCL (aCL-IgG) titers. We measured at followup: repeat aCL-IgG, IgM aCL (aCL-IgM), antibodies to beta2-glycoprotein I (anti-beta2-GPI), lupus anticoagulant (LAC) antibodies, protein C, protein S, activated protein C resistance, factor V506 Leiden mutation, methyl tetrahydrofolate reductase (MTHFR) C677T genotype, and prothrombin 20210A gene mutation. Thrombotic events were confirmed.', 'At recruitment, 20 individuals were negative for aCL-IgG and 67 were positive (22 low, 20 intermediate, and 25 high titer). Twenty of the 87 participants had experienced a previous thrombotic event: 4 in the aCL-IgG negative group and 16 in the aCL-IgG positive group. Among the 87 individuals, the number of those with concomitant prothrombotic risk factors was as follows: 5 had no other prothrombotic risk factors, 32 had 1 risk factor, 24 had 2 risk factors, 10 had 3 risk factors, 10 had 4 risk factors, and 6 had 5 risk factors. Thrombotic events were observed in 20%, 13%, 33%, 10%, 30%, and 50% of these groups, respectively, and the odds ratio associated with a previous thrombotic event was 1.46 per each additional prothrombotic risk factor (95% confidence interval: 1.003-2.134).'] Is the presence of multiple prothrombotic risk factors associated with a higher risk of thrombosis in individuals with anticardiolipin antibodies?