The majority of blood donations in Trinidad and Tobago are made as replacement by family members or friends. National Blood Transfusion Policy was drafted in 2007 to promote voluntary, repeated donation. The objective of this study is to assess the current rate and reasons for donor deferral, and the aim is to guide the proposed donor education and recruitment programme. A retrospective study of pre-donation deferral of prospective blood donors at the National Blood Transfusion Centre, Port of Spain, Trinidad and Tobago, was conducted. Records of all pre-donation deferrals over a 12-month period were studied. As many as 11,346 pre-donation screening interviews were conducted. There were 4043 (35.6%) deferrals. The most common reasons for donor deferral were exposure to high-risk sexual activity (27.6%), low haemoglobin 22.2% and hypertension 17.5%. Other reasons such as medication, chronic medical illness, tattoos, travel history, recent pregnancy, surgery or presentation outside the accepted age limit caused 33.8% of all deferrals and the majority (34.7%) of male deferrals. Low haemoglobin (44.5%) was the most common reason among females. The rate of deferral of voluntary donors was not significantly different from that for replacement donors (31.7 vs. 35.4%, P = 0.25). This study exposed a lack of public awareness as the principal reason for an unacceptably high rate of donor deferral. Donor education about selection criteria needs to be urgently addressed as an objective of the National Policy. Monitoring and evaluation of deferral rates and reasons could be used as one indicator of the effectiveness of the Policy.