We propose a treatment of coordination based on the concepts of functor, argument and subcategorization. Its formalization comprises two parts which are conceptually independent. On one hand, we have extended the feature structure unification to disjunctive and set values in order to check the compatibility and the satisfiability of subcategorization requirements by structured complements. On the other hand, we have considered the conjunction et (and) as the head of the coordinate structure, so that coordinate structures stem simply from the subcategorization specifications of et and the general schemata of a head saturation. Both parts have been encoded within HPSG using the same resource that is the subcategorization and its principle which we have just extended.