LPS induces both B cell proliferation and differentiation to Ig secretion. By treating stimulated cells for a brief period with staurosporine, and inhibitor of protein kinase C, it is possible to allow continued proliferation but partially inhibit differentiation. Analysis of the molecular basis for the decrease in IgM production shows that the increased transcription of the Ig-H chain gene induced by LPS is abrogated by staurosporine treatment whereas alteration of 3' end processing is not affected. These experiments indicate that LPS continues to mediate its effect on some of the more distal differentiative events through protein kinase C even after initial cell activation.