An experimental investigation of the three-dimensional flow field within a multilobed model turbofan forced-mixer nozzle was conducted. The objective of the study was to provide detailed velocity and thermodynamic state variable data for use in assessing the accuracy and assisting the further development of computational procedures for predicting the flow field within mixer nozzles. Velocity and temperature data suggested that the nozzle mixing process was dominated by large-scale secondary circulations that were associated with strong radial velocities observed near the lobe exit plane. Flow field similarity for variable inlet temperature conditions was also observed, although unanticipated.