ABSTRACT In the United States (U.S.) wide differences exist in the environmental policies that individual states adopt. To better understand the reason for this variation I examine the conditions that shape the roll call voting behavior of state lawmakers on environmental policy proposals. I examine a variety of potential explanatory factors ranging from individual legislator characteristics (e.g., party, ideology and gender) and constituency-level conditions (e.g., citizen ideology, demographic characteristics and industry employment patterns) to indicators of campaign effort (business and pro-environment campaign contributions). Analyses of 22 states across four legislative sessions demonstrate support for many hypothesized effects. Similar to findings at the national level in the U.S. Congress, political party and ideology are identified as strong predictors of voting, but additional factors also have an influence. For example, the political leanings of district voters and activities of environmental interest groups have substantive effects on legislative voting patterns.