Lands administered by the Bureau of Land Management (BLM) cover vast and diverse areas of Montana. As such, BLM lands provide significant habitat to many species of conservation concern within the state. The Butte Field Office is no different and accordingly harbors significant populations of several vascular plant Species of Concern (SOC). Lands managed by the Butte Field Office are scattered across areas of southwestern and central Montana. BLM lands in this area are generally small, isolated parcels, though several large, contiguous blocks of BLM land do occur. Total acres managed by the Butte Field Office are approximately 287,000 acres. The purpose of this report is to document the results of recent surveys for Species of Concern on Butte Field Office lands along with available information on these species' biology, ecology, habitat requirements, etc. Field surveys were conducted by Heritage Program Botany and Ecology staff in 2003-2005. Additionally, data pertaining to all occurrences of known Plant Species of Concern on Field Office administered lands are presented. Plant Species of Concern in Montana include all S1 and S2 taxa along with G3 (Globally vulnerable) taxa. Many of these species are also ranked as "Sensitive" on BLM lands in the state (Bureau of Land Management 2005). See Appendix A for a full description of global and state rank definitions. The field surveys conducted during this project help to provide a clearer picture of the abundance and distribution of these species not only on Butte Field Office lands but across the region. Positive survey results as well as negative (not finding a species in a particular location) survey results both provide valuable information that will be useful for conservation planning and management across BLM lands and other ownerships in the state. Field surveys conducted as part of this study in 2003-2005 documented four new occurrences of Plant Species of Concern, one Astragalus convallarius, two Brickellia oblongifolia and one Physaria saximontana var. dentata occurrence. The discovery of the Brickellia oblongifolia occurrence along Soap Gulch is only the third known extent location in the state, all three occurring on the Butte Field Office. In addition to the discovery of new occurrences, several other SOC occurrences that were revisited resulted in the expansion of the population, discovery of new subpopulations nearby, current population counts/estimates or in the refinement of mapped population boundaries. In total, 33 occurrences of ten vascular Plant Species of Concern are known on the Butte Field Office.