This paper analyzes Mexican cactus diversity to determine those states with high species richness, endemism, and endangerment, which may be important for the conservation of these plants. Relationships between environmental factors and species richness and endemism were also examined. Species richness and number of endemic and endangered species were recorded for each state, along with its total area, temperature, and precipitation. Data were analyzed with simple and multiple linear regressions, and complementarity analysis. Results showed that San Luis Potosi, Coahuila, Nuevo Leon, Oaxaca, Zacatecas, Tamaulipas, and Sonora had more than 100 species. There were significant relationships between species richness and endemism, and species richness and number of endangered species. Nine states had higher species richness than expected according to their total area. The aridity of each state was the environmental factor most significantly correlated with species richness and endemism. Eight states are needed to preserve 80% of the total cactus diversity
