The purpose of this study was to investigate the stress distribution of the abutment and sup-porting tissues according to the slopes and types of the guiding plane of distal extension removable partial dentures. The 3-dimensional finite element method was used and the finite element models were prepared as follows. Model I : Kratochvil type guiding plane with $90^{circ}$ to residual ridge Model II : Kratochvil type guiding plane with $95^{circ}$ to residual ridge Model III : Kratochvil type guiding plane with $100^{circ}$ to residual ridge Model IV : Krol type guiding plane with $90^{circ}$ to residual ridge Distal extension partial denture which right mandibular first and second molar were lost was used and the second premolar was prepared as primary abutment with RPI type retainer. Then 150N of compressive force was applied to central fossae of the first and second molars and von Mises stress and displacement were measured. The results were as follows 1. Model I and Model IV showed a similar stress distribution pattern and the stress was concentrated on the apex of the root of the abutment. 2. The stress was increased and concentrated on mesial side of the root of the abutment in Model II. The stress was concentrated on buccal and mesiobuccal side of the root of the abutment in Model IV. 3. In Model I, the root of the abutment displaced and twisted a little in clockwise. In Model IV, the root of the abutment displaced to distolingually at apical region of the root and mesiobuccally at cervical region of the root. 4. In Model II, the root of the abutment displaced to mesiolingually at apical region of the root and more displaced and twisted in counterclockwise at cervical region of the root. In Model III, the root of the abutment displaced to mesiobucally at apical region of the root and more displaced and twisted in clockwise at cervical region of the root.