This paper describes the study aimed at validating the Portuguese version of the MOS SF-36 instrument of assessment. It starts by presenting the results of the implementation of this instrument in a sample of 930 pregnant women and the results of scaling tests, including the values of internal consistency and reliability. However, since a reliable instrument is not necessarily a valid one, the results of several validity tests are also presented. Finally, this paper ends by recommending the use of the Portuguese version of the SF-36 instrument of assessment.