BIAX-1 is a general purpose computer program to evaluate uniaxial and biaxial strength and deformation characteristics of reinforced concrete (R/C) sections. The program computes these characteristics based on the assumption that plane sections remain plane after the application of loading. The program can be used to compute strength or moment-curvature relations for uniaxial or biaxial monotonic loading of reinforced concrete sections. Nonlinear material models are used for both the reinforcing steel and the concrete. The model for the stress-strain behavior of the reinforcing steel is versatile, allowing relations that closely approximate experimentally observed behavior.The program allows two stress-strain diagrams for concrete (unconfined and confined) and four relations for reinforcing steel. The R/C section is described as a combination of rectangular subsections; therefore the program allows easy generation of T, L, or barbell shaped sections. The program user specifies a mesh for each subsection. An iterative procedure (simple bisection algorithm) is used to obtain a solution for the prescribed problem.