The World Health Organization (WHO) estimates the prevalence of a disabling hearing loss to be above 5% world-wide 1. A treatment with a hearing aid - be it behind-the-ear (BTE), in-the-ear (ITE) or receiver-in-canal (RIC) - involves some degree of occlusion of the external ear canal. In many cases, this so-called occlusion effect (OE) leads to an unfamiliar perception of the hearing aid user’s own voice. This fact represents a limiting factor regarding the acceptance of hearing aids by potential users. This thesis focuses on modeling the physical occlusion effect caused by hearing aids and the investigation of active control approaches mitigating this adverse effect. A simple model based on audiological transfer functions is presented, discussed and validated in the first part of the thesis. This model is subsequently used as a basis for the analysis and the synthesis of an active control approach based on sound pressure feedback. The objective and subjective validation of this approach implemented as a prototype setup in a user-study is presented. Finally, the use of the insights from the first part for fitting a hearing aid incorporating such active occlusion control is suggested.