Factors significantly associated with a reduced QoL were pain rate and social circumstances defined as educational level and occupation. Interestingly, pain rate was only associated with a reduced MCS, whereas the social circumstances of the patients were related to the PCS. These data suggest that frequent painful and unpredictable crises are an important psychological burden rather than a physical burden to sickle cell patients as has been suggested previously [12] . In contrast, social circumstances as reflected by occupation and level of education were mainly related to the PCS, suggesting that only patients in good physical performance are able to finish school and find jobs independently of the frequency of admission for painful crises. This was further supported by the finding that no correlation between the MCS and PCS was found in the sickle cell population, which is in contrast to letters the findings of QoL assessments in healthy individuals [7] . Similar to previous findings of McClish et al. [10] , we did not find a correlation between genotype and QoL scores. Also, no difference in QoL scores was observed between patients on hydroxyurea and those who are not on hydroxyurea. This might be explained by the fact that in our study population, hydroxyurea was only prescribed to reduce painful crises and the occurrence of acute chest syndrome. By reducing these complications in patients with an otherwise more severe clinical presentation, hydroxyurea may have improved the QoL. This is in line with a previous prospective study of Ballas et al. [13] who demonstrated an improved QoL with the use hydroxyurea.