Testicular Germ Cell Tumor (TGCT) is the most common malignant tumor in young Caucasian men with an annual increase of 3-6% in the past 50 years. Data in the literature indicate that both environmental and genetic factors acting on the primordial gonocyte/gonocyte are implicated in the etiopathogenesis of this tumour. Genetic linkage and genome-wide analyses did not reveal a major gene effect so far, implying that multiple loci must contribute to the development of TGCTs. Only one significant genetic risk factor has been reported, the so called "gr/gr" deletion of the Y chromosome which still request further confirmation by independent studies. On the other side, the analysis of somatic genetic changes through mutation and genome imbalance analyses and expression profiling has just began to unravel the complex interaction of multiple pathways involved in TGCTs. This review focuses on genetic factors (both genomic and somatic) involved in the etiology, progression and treatment sensitivity of TGCTs.