Four methods used for the production of leucocyte-poor blood were compared: liquid nitrogen recovery and washing, washing alone, the Imugard filter and the Leuko-Pak filter. Twenty units of blood were tested by each technique. Liquid nitrogen recovery and washing, and the Imugard filter removed over 95% of white cells, and 95% and 56% respectively of platelets. Washing alone was unreliable and removed on average 47% of white cells and 85% of platelets. The Leuko-Pak filter removed on average 42% of white cells and 79% of platelets.