This paper presents work in progress for development of an on-line method based on PID (Photo Ionization Detector) for quantitative measurement of tar from biomass gasification. To calibrate the method the PID signals are compared to quantitative data of individual tar compounds obtained by an established reference method. The measured response factors for the model tar compounds demonstrated very good linearity. The PID approach was tested on-line with real producer gases from an atmospheric fluidized bed gasifier operated at 800-900 degrees C. The results suggest that PID can be used for continuous on-line tar measurement of product gases from biomass gasification. (C) 2010 Elsevier B.V. All rights reserved.