Abstract Spontaneous in vitro T cell rosette formation at room temperature leading to enrichment of B cells has been reported. We tested 10 individual New Zealand White rabbits sequentially, separating the lymphocytes either at room temperature or at 37°C. T cells are lost constantly at room temperature but to a lesser extent at 37°C. The determination of the yield of lymphocytes after Ficoll separation gives the best control for the accuracy of the results. If lymphocytes are separated at 37°C and if the yield of lymphocytes is greater than 45%, the variation in T cells is small and their number is constant between 62 and 74%. These data show that the reported wide range of T cells in rabbit peripheral blood is due to methodological errors and not inherent in the rabbit.