Abstract: The subject invention discloses a method for determining the prognosis and probable clinical course of a subject diagnosed with B-CLL. Specifically, the invention involves comparing CD38 expression in a biological sample from the subject containing B-CLL cells to a baseline level of CD38 expression, wherein an elevated level of CD38 expression in relation to the baseline level of CD38 expression may indicate poor prognosis or aggressive course of disease in the subject. Also disclosed is a method for determining whether the Ig V genes of the B-CLL cells of a B-CLL patient are mutated, comprising comparing CD38 expression in a biological sample from the subject containing B-CLL cells to a baseline level of CD38 expression, wherein a lower level of CD38 expression in relation to the baseline level indicates IG V gene mutation.