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Rationale: Coronary artery disease (CAD) is a complex phenotype with multiple genetic and environmental risk factors. The circulating monocyte plays a key role in CAD and contributes to atherogenesis, plaque progression and atherothrombosis, especially through its interactions with platelets. This study tested the hypothesis that gene expression profiling of monocytes in a resting state, and following platelet-mediated stimulation would identify novel molecules that may determine the inherited risk of CAD. Methods: Four groups of subjects were recruited: patients with a premature MI (PMI) <65 years (n=19) and age/gender matched healthy controls (n=19), healthy young men with a strong family history of PMI (n=22) and matched controls with no significant family history of CAD (n=17). Monocyte RNA was extracted before and after platelet-mediated stimulation (for 4 hours) from all subjects for whole genome microarray analysis. Differentially expressed genes were validated by QPCR and those genes with similar trends in expression in the PMI patients and the healthy young men with a family history of PMI were selected for further analysis. These were tested in silico in CARDIoGRAM, a large scale genome wide association study (GWAS) to identify genetic variants that showed either strong associations with CAD or with gene expression in monocytes (expression quantitative trait locus - eQTL). Results: This work revealed similar trends in differential expression of specific monocyte genes between PMI patients and healthy men with a strong genetic risk of PMI compared with their respective healthy controls. These include genes implicated in lipid metabolism (ACAD10), sterol transport (CYP27A1, ARV1) and inflammation (CCL3, EGR1). Of these, ACAD10 and CYP27A1 were the genes which were most statistically significant. In the follow-up analysis of these genes, a genetic variant (rs2238151) in ACAD10 showed a significant association with risk of CAD (risk allele frequency (RAF): 0.63, OR: 1.08, corrected p: 5.85x10[superscript -6]) and MI (RAF: 0.57, OR: 1.09, corrected p: 6.24x10[superscript -6]) in the CARDIoGRAM GWAS meta-analysis and a variant in CYP27A1 (rs933994) was noted to be an eQTL for CYP27A1 expression in monocytes (p=2.9x10[superscript-70]). Conclusions: Gene expression profiling in resting and stimulated monocytes from subjects with premature CAD and those with an increased genetic risk of CAD have revealed novel gene variants which associate with susceptibility to CAD.