Site-specific management of inputs in agricultural production is receiving increasing attention because of new technologies and concerns about excessive input use. This paper provides a microeconomic analysis of its implications. It shows that profit decreases with an increase in the variability of input requirements, but that the input and production effects can be quite complicated. The effects of moving from uncertainty about input requirements to variable requirements are also identified. An empirical study of nitrogen fertilization suggests that sitespecific management may reduce input use substantially, but the production and profitability impacts may not be large.