Three mRNA species for human muscle phophofructokinase containing heterogeneous 5' untranslated sequences were identified through cDNA cloning. Type A mRNA was essentially the same as that reported previously (Nakajima, H., et al. (1987) FEBS Lett. 223, 113). Type B mRNA was considered to be the major gene product, which contained an extra non-coding sequence within the 5' untranslated region of type A mRNA. Amplification of mRNA by polymerase chain reaction revealed that types A and B mRNAs shared a common precursor RNA, and were alternatively spliced. Type C mRNA, homologous to the cDNA sequence from a placenta library (Sharma, P. M. et al., (1989) Gene 77, 177), was considered to be under the control of an alternative promotor.