In a Bureau of Mines study of the Ti-tin phase system, solid single- phase regions were formed at various temperatures by interdiffusing ti and tin. The diffusion profiles were examined quantitatively by scanning them with an electron microprobe analyzer. This method delineated compositional gradients and limits of the single-phase regions and gave a basis for calculating diffusion parameters for the germane phases. Results of this approach differ from diffusion data previously reported for the system because compositions in this instance were directly analyzed and then were used to infer a modification of the phase diagram, whereas prior practice was to infer compositions from a preexisting phase diagram that is now known to be inaccurate in certain details. Considerations of this difference and its implications led to a strong suspicion that the e- phase nitride may have been either mistaken for the s-phase or lumped together with the a-phase in earlier calculations of diffusion parameters. Judicious caution should therefore be exercised in applying the existing diffusion parameters or in trying to clarify the situation.