Assuming Grosu’s (1973) decomposition of Ross’s (1967) Coordinate Structure Constraint into the Conjunct Constraint and the Element Constraint, this article searches for a principled account for the Conjunct Constraint, rebaptized as the Coordinand Constraint. It defends the proposal that different families of effects of the Coordinand Constraint are related to different factors: (a) the lexical information provided by a coordinator, (b) the economy of syntactic displacement operations, and (c) an interface condition prohibiting self-coordination. These three factors are not primitive, but derive from Chomsky’s (1991) Least Effort Principle. Therefore, the Coordinand Constraint is deduced, ultimately, from the Least Effort Principle.