Multilateral (ML) wells account for only a small fraction of the total number of wells drilled today. One reason may be that the economic benefit of drilling ML wells is in question, even though the higher construction costs usually can be justified by the projected increase in productivity. Factors that contribute to the economic success include reservoir characteristics, production and facility capabilities, operator and service company experience with hit installations, technological advances and refinements in the ML drilling and completion system, complexity of the drilling program, and effective contingency planning before beginning drilling operations.