Context:Detailed reports of red cell alloantibody frequencies and specificities in the Thai population are limited. The aims of this study were to determine the specificity and compare the frequency of alloantibodies detected using column agglutination technology (CAT) and conventional tube techniques in blood donors and previously transfused patients.Settings and Design:We retrospectively reviewed antibody screening and identification records for two time periods: January-December 2006 during which conventional tube techniques were used and January 2008-December 2009 when CAT was used.Results:The overall prevalence of alloantibodies in both patients and donors when using conventional tube techniques was 0.7%, for patients only was 0.9% and donors 0.6%. The most frequent antibodies detected in both groups were anti-Lea, anti-Mia, anti-Leb, anti-P1 and anti-E. When using CAT, alloantibodies were found in 0.8% of patients and 0.13% of donors with the five most common alloantibodies found in patients were anti-Mia, anti-E, anti-Lea, anti-c and anti-Leb respectively. Similarly the common alloantibody specificities in donors were anti-Lea, anti-Mia, anti-Leb, anti-M and anti-D.Conclusions:One of the most commonly identified alloantibodies in the Thai population studied was anti-Mia suggesting that Mia positive red cells should routinely be included in antibody screening and identification in this population. For antibody screening and identification, CAT method detected immune and warm alloantibody (ies) more frequently than that associated with conventional tube techniques.