Objectives: Higher side-to-side asymmetry among female athletes compared to their male counterparts during bilateral athletic tasks such as landing from a jump has been proposed as a potential source of non contact knee injuries. However, the kinematic symmetry and potential sex differences during the initial (and most dangerous) phase of bilateral landings have not been examined. The objective of this project is to evaluate lower extremity kinematic asymmetry among recreational athletes during forward jump landing and drop landing tasks. Design: Repeated measures laboratory experiment. Methods: Thirteen male and 15 female athletes performed landing tasks on a force plate while kinematic data were collected. Kinematic asymmetry between legs was calculated for the initial phase of landing for lower extremity kinematics. ANOVA tests and effect size calculations were used to measure the effect of sex, landing task and their interaction on kinematic asymmetry. Results: Athletes exhibited higher asymmetry for knee valgus (d=0.5, p=0.006) and hip adduction (d=0.5, p=0.057) when performing forward compared to drop landings. Females landed with greater knee valgus asymmetry than males during forward landings (d=0.7, p=0.078) and with greater ankle abduction asymmetry during drop landings (d=0.5, 0.091). Conclusions: Female athletes exhibited greater frontal plane knee and ankle kinematic asymmetry than males during forward landings which may be related to the higher rate of ACL injury. Forward landings elicited greater hip adduction and knee valgus asymmetries than drop landings and, therefore it may be more appropriate for field testing when screening for asymmetries. �� 2011 Sports Medicine Australia.