Conversion of potential organ donors to actual donors is negatively influenced by family refusals. Refusal rates differ strongly among countries. Is it possible to compare refusal rates in order to be able to learn from countries with the best practices? We searched in the literature for reviews of donor potential and refusal rates for organ donation in intensive care units. We found 14 articles pertinent to this study. There is an enormous diversity among the performed studies. The definitions of potential organ donors and family refusal differed substantially. We tried to re-calculate the refusal rates. This method failed because of the influence caused by the registered will on donation in the Donor Register. We therefore calculated the total refusal rate. This strategy was also less satisfactory considering possible influence of the legal consent system on the approach of family. Because of lack of uniform definitions, we can conclude that the refusal rates for organ donation can not be used for a sound comparison among countries. To be able to learn from well-performing countries, it is necessary to establish uniform definitions regarding organ donation and registration of all intensive care deaths.