- UML (Unified Modeling Language) is a collection of somewhat overlapping modeling techniques, thus creating a difficulty in establishing practical guidelines for selecting the most suitable techniques for modeling OO artifacts. This is true mainly with respect to two types of interaction diagrams: Sequence and collaboration. Attempts have been made to evaluate the comprehensibility of these diagram types for various types of applications, but they did not address the issue of quality of diagrams created by analysts. This article reports the findings from a controlled experiment where both the comprehensibility and quality of the interaction diagrams were investigated in two application domains: management information systems (MIS) and real-time (RT) systems. Our results indicate that collaboration diagrams are easier to comprehend than sequence diagrams in RT systems, but there is no difference in comprehension of the two diagram types in MIS. Irrespective of the diagram type, it is easier to comprehend interaction diagrams of MIS than of RT systems. With respect to diagram quality, in the case of MIS, analysts create collaboration diagrams of better quality than sequence diagrams, but there is no significant difference in quality of diagrams created in RT systems. Irrespective of the diagram type, more correct diagrams are created in MIS applications than in RT applications.