A Physical Electronics 595 Scanning Auger Microprobe was used to study etched filaments and transverse sections of variously reacted commercial bronze matrix multifilamentary Nb3Sn conductors. Using beams as fine as 100 nm, tfn concentration profiles were observed in polished samples. Differences were noted in the shape of the tin gradient as a function of the location of the reacted filaments with in the wires. The tin content of the bronze was also measured between pre-reacted filaments in an unreacted composite and found to be about 1 at.% lower than in the large bronze reservoirs. In a Harwell composite with P-poisoned niobium diffusion barriers, P was detectable in the Nb3Sn formed on the barrier but not on the filaments.