Applying Bandura's social learning theory, this paper proposes a theoretical framework for analysing the effect of MUD playing on users' self efficacy. Three types of self efficacy – computer self efficacy (CSE), social self efficacy (SSE) and generalized self efficacy (GSE) – are introduced. A possible hypothesis – successful performance, vicarious experience, hearing positive verbal persuasion and massive exposure during MUD playing will raise the CSE, SSE, and GSE of users – is suggested. Finally, a theoretical model explaining the relationship between self efficacy and MUD activities is proposed. Applicant la theorie de l'apprentissage de Bandura cet article propose un cadre theorique pour analyser les effets de MUD jouant sur l'efficacite personnelle de l'utilisateur. 3 types de celles-ci - computer self-efficiency (CSE) social self efficacy (SSE) et generalise self-efficiency (GSE) - sont introduits et une hypothese possible. Les resultats reussis, experience substituee, ecoute de la persuasion verb...