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Nine plant growth models for grassland ecosystems were examined. Model objectives, complexity and inclusiveness were compared. A large degree of diversity in model complexity and structure exists in grassland models. The models examined during this comparison consisted primarily of linear and nonlinear difference/differential equations. Though grassland models use many of the same concepts of other plant growth models, grassland models tend to be more concerned with moisture and nutrient status then their cropland counterparts. The system level models require large amounts of data to use, yet these data are often unavailable and parameters are hard to establish. These models seem best suited to merely approximate system behavior, but it will become extremely useful as more understanding of the grassland ecosystem is gained. Grassland models which combine plant growth with animal grazing tend to include spatial heterogeneity of vegetation, thereby allowing these models to simulate multiple landscape points and patchy grazing by herbivores.