Coupling is an internal software attribute that can beused to indicate the degree of interdependence among thecomponents of a software system. Coupling is thought tobe a desirable goal in software construction, leading to bettervalues for external attributes such as maintainability,reusability, and reliability. Aspect-oriented software development(AOSD) is a new technique to support separation ofconcerns in software development. In aspect-oriented (AO)systems, the basic components are aspects or classes, whichconsist of attributes (aspect or class instance variables) andthose modules such as advice, intertype declarations, pointcuts,and methods. Thus, in AO systems, the coupling ismainly about the degree of interdependence among aspectsand/or classes. To test this hypothesis, good coupling measuresfor AO systems are needed. In this paper, we proposea coupling measure suite for assessing the coupling inaspect-oriented systems. We first present a coupling frameworkfor AO systems which specially designed to count thedependencies between aspects and classes in the systems.Based on this framework, we formally define various couplingmeasures in terms of different types of dependenciesbetween aspects and classes. We also discuss the mathematicalproperties of these measures.