DNA extraction from frozen blood clots is challenging. Here, the authors applied QIAGEN Clotspin Baskets and the Gentra Puregene Blood Kit for DNA extraction to cellular fraction of 5.5 ml whole blood without anticoagulating additives. The amount and quality of extracted DNA were assessed via spectrophotometer and gel electrophoresis. Results from array-based genotyping were analyzed. All steps were compared with DNA isolated from anticoagulated blood samples from a separate study. The quality and concentration of DNA extracted from clotted blood were comparable to those of DNA extracted from anticoagulated blood. DNA yield was on average 27 mu g per ml clotted blood, with an average purity of 1.87 (A260/A280). Genotyping quality was similar for both DNA sources (call rate: 99.56% from clotted vs 99.49% from anticoagulated blood). METHOD SUMMARYThis study describes DNA extraction from frozen clotted blood using QIAGEN Clotspin Baskets and the Gentra Puregene Blood Kit. The concentration, yield per milliliter of blood, purity and integrity of the DNA were further confirmed via spectrophotometer and gel electrophoresis. In addition, performance for genotyping on the Illumina Global Screening Array was analyzed. Comparisons with DNA extracted from anticoagulated blood were performed.