Decriminalization under State law has meant the reduction, not the elimination, of penalties for possessing marijuana. The modest achievement of these reforms is due partly to the relative power of forces advocating and opposing decriminalization. A review of marijuana decriminalization laws enacted in 1975-76 reveals that factors contributing to their passage were the support of at least one important law enforcement group or the neutrality of such groups, the Governor's nonparticipation, the perceived success of Oregon's experience, the media's objectivity, and active involvement and support of respected legislative leaders. In none of the States actually passing decriminalization laws did the issue become controversial. Studies demonstrating that moderate marijuana use was relatively harmless and organized lobbying by advocates had no significant effect on the legislative process. The failure of the U.S. Congress to pass legislation decriminalizing marijuana possession under Federal Statutes may be one reason why the decriminalization movement has not progressed further. Other reasons may be insufficient public support and interest in more reforms, the absence of powerful lobbying for marijuana reform because the movement can offer little in return for its support, and the fact that marijuana is favored by youth rather than middle-class adults dominating society. The current political climate suggests an uncertain future for marijuana decriminalization. The paper includes 21 footnotes.