Designers of interactive learning environments face the issue of managing the learner's cognitive load, reducing irrelevant sources while optimizing useful sources of load. I propose a conceptual framework aimed at organizing the contributions of the papers presented in this special issue. The framework identifies three main dimensions, namely individual, task and environment, which may have specific or combined effects on the amount and type of cognitive load experienced during learning activities. I summarize some of the findings presented in the special issue with respect to each of these dimensions. Then I discuss some limitations of the studies and some perspectives for further research in the domain. I emphasize the need to control learners' level of familiarity with the task setting and environment features, not just their prior knowledge of the content area, in order to obtain reliable assessments of cognitive load and learning outcomes. (Contains 1 figure and 1 table.)