Occlusion effect (OE) is mainly caused by increasing low frequency gain at the ear drum. It can be controlled by modifying the vent length of hearing aids. Small venting is caused by the size of ear canal such as CIC hearing aids. It is known to hard to control OE in this case. However, it is suggested that a tight fit of the bony portion in the ear canal can reduce OE. The management of OE in CIC hearing aids through a tight fit is discussed in this article. KEY WORDS：Completely-in-the-canal (CIC)·Hearing aid fitting·Occlusion effect·Tight fit·Vent.