INTRODUCTION The effectiveness of flame modifications in reducing NOx emissions from package boilers is presently being investigated in a three-phase program. During Phase I@ a versatile oil-fired facility was designed and constructed to serve as an experimental arena for investigating control techniques(1) (a sketch of the facility is shown in Figure 1)@ The present report documents the work of Phase II which utilized the experimental facility in a systematic investigation of burner modifications@ flue gas recirculation@ and staged combustion as methods of emission control for oil-fired package boilers. During the testing@ control techniques were sought that require both minor modifications (applicable to existing boilers) and extensive modifications (primarily applicable to a redesign of new boilers). Having determined promising emission control techniques during the activities of Phase II@ we recommend that these techniques be applied to actual field operating boilers during Phase III.