 We used the polymerase chain reaction (PCR) to detect ALL1-AF4 rearrangements, the molecular hallmark of t(4;11) in a series of 46 pre-pre-B (CD19+, CD24+, CD10/CD20/cylgM/sIgM-) acute lymphoblastic leukemias (ALL).     ///    "Moreover, reciprocal der (4)-derived AF4-ALL1 transcripts were observed in 65% of the cases analyzed. "    ///    Pre-pre-B acute lymphoblastic leukemia: high frequency of alternatively spliced ALL1-AF4 transcripts and absence of minimal residual disease during complete remission..     ///    "In contrast, only two patients from a group of 67 common (CD19/CD10+, cylgM/sIgM-) and pre-B ALLs (CD19/cylgM+, CD10 +/-, sIgM-) showed ALL1-AF4 mRNA. "    ///    "Eight of the 18 pre-pre-B ALL patients with an ALL1-AF4 recombination are currently in complete continuous remission for up to 54 months (median, 26 months). "    ///    Overall this study documents a similarly high incidence of ALL1-AF4 recombinations in children (infants excluded) and adults with pre-pre-B ALL and demonstrates the decline of the leukemic cell clone below the detection level of PCR in a remarkable proportion of patients under intense treatment protocols.. 