RT-PCR products of wt1 during follow-up of a patient with AML achieving CR and who relapsed 14 months later. The PCR products were additionally quantitated by a competitive PCR. Marker, HindIII/EcoRI-digested λ DNA; lane 1, negative control; lane 2, positive control; lane 3, de novo AML at diagnosis (19.0371 fg wt1-specific mRNA/μg total RNA); lanes 4 through 7, AML in CR (wt1 mRNA <0.0001 fg/μg); lane 8, AML in clinical and morphological CR but positive PCR (quantitation due to limited amount of RNA not done); and lane 9, clinical and morphological relapse of AML (9.484 fg/μg).