Evolution of communication technology has enabled the educational community to interact synchronously or asynchronously with almost equal ease. Many instructors feel that synchronous interaction is the epitome of learning, while others feel that asynchronous interaction offers better learning opportunities. This paper uses the Delphi Technique in an attempt to arrive at an indication of whether instructors favor one interaction mode above the other. Eight experienced distance education instructors were interviewed for their opinions on the interaction types that are considered essential in online learning environments. The results show a predominant preference for the asynchronous mode for all types of interaction and a strong preference for teacher-learner interaction in the synchronous mode. The nature of interaction and the following eight categories of interaction ranked by the experts are discussed in detail: synchronous learner-material interaction; synchronous learner-self (reflective) interaction; synchronous learner-learner(s) interaction; synchronous teacher-learner interaction; asynchronous leaner-material interaction; asynchronous learner-self (reflective) interaction; asynchronous learner-learner(s) interaction; and asynchronous teacher-learner interaction. Three tables contain: experts' responses as to types of interaction essential in online learning; types of interaction ranked according to importance in online learning; and types of interaction according to revised rankings of importance in online learning. (Author/DLS)