Case-control studies, which serve as standard design for genetic association analysis, can be the most practical and powerful approach to detect genetic polymorphisms contributing to susceptibility to complex human diseases. However, considerable concern has been expressed that this approach is prone to population stratification, which can lead to biased or spurious results. We review several methods to detect and account for population stratification; these methods include nuclear family-based transmission/disequilibrium test (TDT), and genomic control (GC) and structured association (SA) based on unlinked genetic markers.