Background. The discovery of the Human Herpes virus 8 (HHV8) improved our knowledge of the pathogenesis of Kaposi s sarcoma. After organ transplantation, Kaposi s sarcoma exhibits distinctive features compared with other forms of the disease. Patients and methods. We report 22 cases of post-transplant Kaposi s sarcoma (12 kidneys, 2 kidney-pancreas, 6 livers and 2 hearts). The aim of this retrospective study was to analyze clinical and virological characteristics in these transplant patients and to specify the frequency of HHV8 seroconversions in this population. Results. Twenty-one patients showed cutaneous lesions and 9 had visceral involvement. HHV8 serology was positive in 16/20 patients at transplantation and in 21/22 cases at the time of Kaposi s sarcoma diagnosis. Most cases corresponded to viral reactivations whereas seroconversions occurred in 2 cases and may have been linked to viral transmission by the graft. Treatment led to recovery in 68p. 100 of the cases. Two heart-transplant patients died from their disease. We included in our series two cases of re-transplanted patients without recurrence of Kaposi s sarcoma and one case of familial Kaposi s sarcoma. Discussion. Seroconversions after transplantation emphasize the interest of systematic screening of HHV8 serology in transplant recipients and their donors. Background. The discovery of the Human Herpes virus 8 (HHV8) improved our knowledge of the pathogenesis of Kaposi sarcoma. After organ transplantation, Kaposi sarcoma exhibits distinctive features compared with other forms of the disease. Patients and methods. We report 22 cases of post-transplant Kaposi’s sarcoma (12 kidneys, 2 kidney-pancreas, 6 livers and 2 hearts). The aim of this retrospective study was to analyze clinical and virological characteristics in these transplant patients and to specify the frequency of HHV8 Twenty-one patients showed cutaneous lesions and 9 had visceral involvement. HHV8 serology was positive in 16/20 patients at transplantation and in 21/22 cases at the time of Kaposi sarcoma diagnosis. Most cases housed to viral reactivations were seroconversions occurred in 2 cases and may have been linked to viral transmission by the graft. Treatment led to recovery in 68p. 100 of the cases. Tw o heart-transplant patients died from their disease. We included in our series two cases of re-transplanted patients without recurrence of Kaposi’s sarcoma and one case of familial Kaposi’s sarcoma. Discussion. Seroconversions after transplantation emphasizing the interest of systematic screening of HHV8 serology in transplant recipients and their donors.