In vitro viability of B-CLL cells is related to p27 level of expression. Lymphoid cells from 31 B-CLL patients were cultured up to 5 days in RPMI+ 10% FCS. Viability was assessed by trypan blue exclusion. For each time point, the percentage of viable cells was calculated. Data are presented as means ± standard deviation comparing 19 samples of high and 12 samples of low p27 expressing cells. When cultured in vitro, B-CLL cells expressing higher p27 levels had sustained viability as compared with cells expressing low p27 levels.