We develop a theory of monotone comparative statics for models with adjustment costs. We show that comparative-statics conclusions may be drawn under the usual ordinal complementarity assumptions on the objective function, assuming very little about costs: only a mild monotonicity condition is required. We use this insight to provide a general treatment of the le Chatelier principle based on adjustment costs. We extend these results to a fully dynamic model of adjustment over time: given only minimal structure on costs, optimal adjustment follows a monotone path. We apply our results to models of capital investment and of sticky prices.