We studied the abundance and structure of globin mRNAs present in K562 cells both before and after induction of hemoglobin synthesis by hemin. In vitro translation of poly(A)+ RNA from K562 cells generated protein products corresponding to alpha, A gamma-, G gamma-, epsilon-, and zeta-globin mRNAs. Individual globin mRNAs increased 1.5- to 3-fold after induction. Similar results were obtained by measuring steady-state mRNA concentrations of induced and uninduced cells by using S1 nuclease mapping. Globin gene transcripts were correctly initiated and processed. In addition, S1 nuclease analysis revealed the presence of delta-globin mRNA in both control and induced cells. A small percentage of delta-globin transcripts appeared to be initiated upstream from the normal initiation site. beta-Globin mRNA was not detected in any studies. The results (i) suggest that hemin induction of K562 cells is mediated at a transcriptional level and (ii) reveal the dissociation of delta- and beta-globin gene expression in K562 cells compared with normal erythroid cells.