Interpretation of large-scale color infrared and color aerial photography can be a labor and cost-effective means for inventorying and monitoring rangelands while maintaining accuracy. Ground measurements of vegetation cover at Organ Pipe Cactus National Monument were taken in 1975 and 1984. Large-scale (1:1200) color and color infrared aerial photo estimates were compared to these ground measurements through regression and correlation to check photo accuracy. Relationships between photo estimates and ground measurements of total vegetation and shrub cover were strong when using either film type. Color infrared photo estimates corresponded better with ground measurements for both tree cover and cactus cover than color photo estimates. Large-scale aerial photography is also useful for determining some of the causes of vegetation change. Evidence gathered from both sets of photos suggested that vegetation change at OPCNM was largely the result of domestic livestock removal and short-term climatic fluctuations.