The aim of this research is to describe and analyses the reactions and complications of voluntary blood donors. This thesis are described and voluntary blood donors, their rights and benefits, the history of blood donation and procedures for the examination and blood sampling. The total number of voluntary blood donors, the total number of reported reactions and complications and their distribution by type of donors registered with the Register of reactions and complications of blood donors and the Registry of serious adverse events at the Centre for Transfusion Medicine, University Hospital Center Split over a three year period, 2013. - 2015.. In 2013, there were 18,296 accepted voluntary blood donors, in 2014, 18 784, while in 2015 there were 18,647 accepted. By percentage, are the most common current vasovagal reactions and complications where they were, compared to other responses, 80.70 % represented in 2013, 71.20 % in 2014 and 82.1 % in 2015. The following are then delayed vasovagal reactions and complications which in 2013 represented 10.80 %, 27.40 % in 2014 and in 2015 it was 16.80 %. Other reactions and complications are present in very low proportion. The reactions and complications are more frequent in October, November and December in 2013 and 2014, while in 2015 more frequently in April, May and June. Comparing more and less complications, complications get significantly more prevalent in relation to weight, and are more frequent during blood donation.