We studied 321 patients with AML at diagnosis for the presence of inv(16)(p13q22) and CBF beta/MYH11 fusion transcripts by cytogenetic and RT-PCR techniques respectively.     ///    The observed frequencies of CBF beta/MYH11 fusion transcripts in our study have been adjusted for the reported incidence of each FAB subtype and we calculate that 10.1% of all new cases of AMLs have molecular evidence of inv(16)(p13q22).     ///    Frequency of CBF beta/MYH11 fusion transcripts in patients entered into the U.K.     ///    We conclude that molecular screening for the presence of CBF beta/MYH11 fusion transcripts should be mandatory in all case of AML at diagnosis.. 