Few instruments with attested levels of reliability and validity to study daily stress have been developed. Accordingly, the goal of the present was to evaluate the levels of reliability of the Inventory of daily stress (IDS), of Brantley, Waggoneer, Jones and Rappaport (1987), translated into Spanish, for its administration in Mexico and Spain, taking care of special idiomatic aspects for each sample. The results of the analysis of alphas, to evaluate the reliability, were high in the general sample, and so was the particular analysis for each sample. The results are discussed arguing for the need of instruments with appropriate metric properties for research which give validity to findings.