Abstract: A mortise and tenon joint system for providing miter joints with increased strength and resistance to expansion. The mortise and tenon joint system includes a board member having a first end and a second end, a tenon extending from the first end of the board member, a plurality of channels extending traversely into an outer sidewall of the tenon, and a mortise extending into the second end of the board member having a form similar to the tenon. The tenon includes a base channel, a first channel, a second channel and an end channel. The channels are preferably parallel to one another and preferably completely surround the tenon in a connected manner. The distance between the base channel and the first channel is preferably greater than the distance between the first channel and the second channel.