Background: Although weight bearing lunge exercises are frequently employed during patellofemoral rehabilitation, patellofemoral compressive force and stress are currently unknown for these exercises. Methods: Eighteen subjects used their 12 repetition maximum weight while performing forward and side lunges with and without a stride. EMG, force platform, and kinematic variables were input into a biomechanical model, and patellofemoral compressive force and stress were calculated as a function of knee angle. Findings: Patellofemoral force and stress progressively decreased as knee flexion increased and progressively increased as knee flexion decreased. Patellofemoral force and stress were greater in the side lunge compared to the forward lunge between 80° and 90° knee angles, and greater with a stride compared to without a stride between 10° and 50° knee angles. There were no significant interactions between lunge variations and stride variations. Interpretation: A more functional knee flexion range between 0° and 50° may be appropriate during the early phases of patellofemoral rehabilitation due to lower patellofemoral compressive force and stress during this range compared to higher knee angles between 60° and 90°. Moreover, when the goal is to minimize patellofemoral compressive force and stress, it may be prudent to employ forward and side lunges without a stride compared to with a stride, especially at lower knee angles between 0° and 50°. Understanding differences in patellofemoral compressive force and stress among lunge variations may help clinicians prescribe safer and more effective exercise interventions. © 2008.