The study will include patients with CLL treated with splenic irradiation in Maastro Clinic, Maastricht, The Netherlands, Maxima Medisch Centrum Veldhoven/Catharina hospital, Eindhoven, The Netherlands and Modena hospital, Modena, Italy. Data will be collected from patient records in an uniform database. Data will include demographic data, CLL stadium (RAI and Binet) at diagnosis and at the time of irradiation treatment, clinical data at diagnosis (haematology), splenic irradiation data, follow-up data such as date of progression or death