Gastric cancer is a heterogeneous disease with differing chemosensitivities to anti-cancer drugs. Current selection of standard therapy is often empirical. Gene expression profiling has been shown to have the capability to dissect this heterogeneity allowing for sub-classification and risk-stratification of cancers according to their biological features and clinical outcome. Utilising gene expression data coupled with in-vitro, in-vivo or clinical response data is a promising strategy that may enable clinicians to match the right drug to the right patient.