We examined steady-state levels of mRNA for alkaline phosphatase in neutrophils (NAP) treated with granulocyte colony-stimulating factor (G-CSF). The amount of mRNA for NAP was shown to increase after 6 hours of culture with G-CSF when no increase in NAP activity was yet observed, and the transcript was the greatest after 20-24 h of culture with G-CSF. Treatment of neutrophils with both G-CSF and retinoic acid augmented the amount of mRNA for NAP over the amount obtained by G-CSF alone, which was most marked at 24 h. These results show that both G-CSF-mediated NAP induction and its potentiation by retinoic acid are due to the increased levels of mRNA for NAP.