A convincing association study includes at least appropriate sampling, accurate genotyping, and appropriate statistical analysis (Hattersley et al. 2005). Additionally, association studies require replication in independent populations (Lohmueller et al. 2003). We have followed these rules in a recent study to assess the association between the risk of severe acute respiratory syndrome (SARS) coronavirus infection and the variable number tandem repeat (VNTR) polymorphism in the exon 4 of the L-SIGN gene (for liver/lymph node-specific ICAM-3 grabbing nonintegrin, encoded by CLEC4M) (Zhi et al. 2007). In this study, the individuals of three independent case-control populations have been rigorously selected and all of them are unrelated adults (Zhang et al. 2005). The genotyping of the VNTR polymorphism was performed by separating PCR products on agarose gel. As for the statistical analysis, we have used widely accepted methods to evaluate Hardy-Weinberg equilibrium, compare allele or genotype frequencies, and assess the genetic association. By use of this protocol for an association study, we found that there is lack of support for a genetic association between the L-SIGN polymorphism and risk of SARS coronavirus infection, which was previously reported by Chan et al. (Chan et al. 2006; Zhi et al. 2007).