I was asked to come here and give an educational overview talk on the recent work that has been done in the x-ray residual stress area and some of. the reasons why it is not always accepted as a val1d technique. The main problem that we have.to lo?k at is that when anyone measures macroscop1c resldual stresses, by whatever method - mechanical. techniques, x-ray techniques, ultrasonic technlquesone is always-measuring a different property of the material and trying to relate that to the macroscopic residual stress. There is no reason that residual stress must be the same for all these particular techniques. People get upset when the x-ray technique does not coincide with mechanically measured values, but there are definite reasons why it doesn't, and I want to go through some of those reasons. Measurements of residual stress by x-ray is a diffraction technique - it's not a radiography technique. I want to go through the principle~ very quickly and then emphasize some of the recent lnstrumentation advances developed in the last couple of years. Then I want t~ use the remaining time to discuss the situations where the validity of the x-ray technique is sometimes questioned.