A new diode-pumped Nd:YAlO3 laser system emitting pulse bursts at 671 nm has made it possible to apply tracer laser induced fluorescence (LIF) techniques for spray diagnostics not only by using model fuels but in real diesel or gasoline fuel sprays. In this work we characterize possible candidates for LIF tracers that can be excited in the wavelength region of 650-680 nm where com. diesel fuel is transparent. Two fluorescent dyes, Rhodamine 800 and Atto 680, were identified as possible tracers and tested for their relative fluorescence quantum yield and absorption cross section in a diesel fuel environment as well as their behavior at different temps. First results of laser drop sizing expts. with Rhodamine 800 as a fluorescence tracer are presented.