Alpha-particle therapy has received increased attention during the last few years because of the development of new targeting constructs and new labeling techniques and the availability of suitable α-particle - emitting radionuclides. This work provides an overview of methods that have been used in clinical trials in estimating the absorbed dose to tumors and healthy tissue in patients following such α-particle therapy. Similarities and differences compared to conventional therapies using β¯-particle emitters are presented. The specific challenges of establishing accurate dosimetry for α- particles in the individual patient are also discussed, as is the effect that improved patient-specific dosimetry might have on the overall efficacy of this type of therapy.