Tuberculosis, a potentially fatal infectious disease, affects millions of individuals annually worldwide. Human protective immunity that contains tuberculosis after infection has not been clearly defined. To gain insight into host genetic factors, nonparametric linkage analysis was performed using high-throughput microarray-based single nucleotide polymorphism (SNP) genotyping platform, a GeneChip array comprised 59 860 bi-allelic markers, in 93 Thai families with multiple siblings, 195 individuals affected with tuberculosis. Genotyping revealed a region on chromosome 5q showing suggestive evidence of linkage with tuberculosis (Z(lr) statistics=3.01, logarithm of odds (LOD) score=2.29, empirical P-value=0.0005), and two candidate regions on chromosomes 17p and 20p by an ordered subset analysis using minimum age at onset of tuberculosis as the covariate (maximum LOD score=2.57 and 3.33, permutation P-value=0.0187 and 0.0183, respectively). These results imply a new evidence of genetic risk factors for tuberculosis in the Asian population. The significance of these ordered subset results supports a clinicopathological concept that immunological impairment in the disease differs between young and old tuberculosis patients. The linkage information from a specific ethnicity may provide unique candidate regions for the identification of the susceptibility genes and further help elucidate the immunopathogenesis of tuberculosis.