Pyruvate kinase (PK) has four isozymes (L, R, M1, M2) that are encoded by two different genes. Among these isozymes, abnormalities of liver (L)-type PK is considered to be associated with hereditary nonspherocytic hemolytic anemia in humans. We isolated and determined the full-length sequence of human L-type PK cDNA. The cDNA contains 1629 base pairs encoding 543 amino acids, 68 base pairs of 5'-noncoding sequence, and 734 base pairs of 3'-noncoding sequence. The similarity between human and rat L-type PK was 86.9% at the nucleotide sequence level and 92.4% at the amino acid sequence level. The full-length L-type PK cDNA was placed under the promoter of simian virus 40 and introduced into monkey COS cells. Human L-type PK activity was detected in the extract of COS cells by the classical PK electrophoresis method.