Cellular SET protein levels correlate with parameters of CLL progression. The time from diagnosis to first needed treatment (TTT) was assessed relative to SET protein levels in CLL cells as determined by quantitative immunoblotting. Patients with high levels of SET were compared with those with low levels of SET for (A) the β-isoform, (B) the α-isoform, (C) the total (α + β) SET, and (D) the numerical ratio of the α-isoform and β-isoform (α/β ratio) (n = 285). Those with high SETα, high total SET(α + β), and high α/β ratios had statistically significantly shorter TTT. The OS for patients with high levels of SET were compared with those with low levels of SET for (E) SETβ, (F) SETα, (G) total SET(α + β), and (H) the numerical ratio of the α-isoform and β-isoform (α/β ratio) (n = 285). The OS was significantly shorter in patients with high α/β ratios of the SET isoforms (n = 285).