The 1984 cost/benefit model for the evolution of carnivorous plants addresses their potential energetic and ecological advantages. It has provided a conceptual framework for research on distribution, variation in trap allocation and mechanisms, association with low rates of photosynthesis and whole-plant growth, and ecology of carnivorous plants relative to noncarnivorous ones. We re-assess this model, its potential extensions, and the validity of its assumptions and predictions. We review what is known about photosynthesis, respiration, relative growth rates, and resource allocation in carnivorous and noncarnivorous plants, and growth, nutrient limitation and stoichiometry, adaptation to different prey, and optimal trap allocation of carnivorous plants. We propose explanations for six ecological and evolutionary paradoxes involving carnivorous plants. Future advances will hinge on better quantification of the cost/benefit model and comparing model predictions with data.