DiGeorge syndrome (DGS) is a congenital anomaly involving developmental defects of the third and fourth pharyngeal pouches. Thymic aplasia or hypoplasia, parathyroid aplasia or hypoplasia, cardiac malformations, and dysmorphic facies are characteristics features. We present a case which had thymic aplasia, hypocalcemia, facial dysmorphism (hypertelorism, low set ears, cleft of soft palate, fish-like mouth and micrognathia) and congenital heart disease (ventricular septal defect, perimembranous type). The T-cell immunologic functions as a percentage of T-cell and phytohemagglutinin stimulation test were within normal range matched with age. Molecular study showed microdeletion of chromosome 22q11.2 by genotype analysis, but chromosome study of high-resolution cytogenetic analysis by G-banding technique was normal. To our knowledge, about 90% of DiGeorge syndrome patients show chromosome abnormalities, most involving chromosome 22 (monosomy of 22q11.2). In the past, most cases were proven by high-resolution cytogenetic analysis or fluorescence in situ hybridization(FISH). We report a case of DGS in Taiwan with microdeletion of chromosome 22q11.2 detected by genotype analysis.