The paper is focused on the experimental determination of residual stresses, using the hole-drilling strain gage method, described by a well known ASTM standard. Some practical difficulties of the experimental technique are emphasized, together with the contingency of obtaining a non-uniform stress distribution, for the studied specimen. As a consequence, a special calculus program is recommended to be used, as presented in the paper. Three possible calculus methods are exemplified, for the selected program. Some differences were observed, when comparing the corresponding residual stress values, and caution is recommended for choosing the suitable method, in any practical situation.