Seminomas represent the most common histological subgroup of all testicular germ cell tumors. About 75% of all seminomas present as clinical stage I disease at time of initial diagnosis and exhibit a long-term cure rate of 99%. Management strategies maintaining these high cure rates but minimizing the risks need are actively pursued. Currently, three treatment strategies are available for stage I seminomas: surveillance, radiotherapy and chemotherapy. Pathohistological prognostic factors allow an individualized risk-adapted therapeutic approach. Tumor size < or =4 cm and absence of rete testis invasion define a low-risk group with a recurrence rate of 12% being best managed by surveillance. Tumor size >4 cm and presence of rete testis invasion define a high-risk with a 35% risk of relapse, best managed by active therapy. Active treatment either consists of radiation of the ipsilateral paracaval or paraaortic lymph nodes with 20 Gy or of adjuvant chemotherapy with 2 cycles of carboplatin. It is currently unclear if 1 cycle carboplatin is as effective as 2 cycles; if this approach is performed follow-up has to be standardized and a compliance of both patient and physician are mandatory.