In concrete buildings, recently the design of column is increasingly determined by architectural,rnaesthetic, and economic criteria leading to slender cross-sections of columns. However, slenderrncolumn design requires rigorous analysis to account second order effect due to deflection of therncolumn. Because the deflection provides additional eccentricity to axial load that inducesrnadditional second order moment. If second order effect is not considered adequately, it can causernstability failure, which is catastrophic. Since exact rigorous analysis demands morerncomputational effort, simplified methods have been proposed in building codes such as EBCS_2,rn1995, CEB_FIP1990 and ACI code still that involves iterative procedure. Moreover, evenrnrecently developed commercial computer programmes such as ETABS and SAP2000 do notrnconsider second order effects due to the deflection of the column between its ends adequately asrncompared to relative deflection between ends of columns.rnIn this thesis, approximate uniaxial P_M interaction diagram for non-sway slender RCrnrectangular column is presented based on the simplified method of EBCS_2, 1995-second orderrneccentricity formula (deflection between two ends of a column) which is rather simple andrnunsophisticated for design of slender column. For the preparation of the interaction diagram,rncross section interaction diagram and column slenderness is used. Since the slender columnrncapacity is smaller than short column capacity, the cross section interaction diagram is modifiedrnso that it would have a room for the slenderness effect. This is made by deducting additionalrnmoment due to second order and geometric imperfection eccentricity from cross sectionrninteraction diagram.rnFinally, the approximate interaction diagram is checked for its validity and satisfactory result isrnobtained. Therefore, the interaction diagram can be used as a design aid as well as preliminaryrncross section capacity estimation since it is very easy and quick method. Moreover, it can be usedrnfor checking of computer output