The Maudsley Obsessional-Compulsive Inventory (MOCI; Hodgson & Rachman, 1977) continues to be a widely used self-report measure of obsessive-compulsive symptoms. It has been translated into at least seven languages and the respective validations have resulted in good psychometric characteristics. It has not been validated to the Portuguese population yet.

To investigate the psychometric properties and factorial structure of the MOCI Portuguese version.

The process of translation/re-translation followed the required steps. The MOCI was administered to a community sample of 217 first year university students (178 girls; 82.0%). The mean age was 18.50 (± 2.345: range: 17–35). To study the temporal stability 166 (135 girls; 81.3%) respondents answered the questionnaires again after approximately six weeks.

The MOCI Cronbach’s a was good (.79). The test-retest coefficient for the total score was high (.79; p<.001). An inspection of the Cattel’s Scree plot and also of the item’s content led us to select a three factors structure, which explained variance was of 29.17%: Factor (F) 1 “Doubting and Rumination” (VE=15.43%; a=.72); F2 “Checking” (VE=7.65%; a=.66) and F3 “Cleaning” (VE=6.08%; a=.63). Temporal stability of F1, F2 and F3 were high: .67, .65 and .73 (all p<.001), respectively. Pearson correlations between factors were moderate and significant (≥.30).

The MOCI Portuguese version has good psychometric properties and its factorial structure is in accordance with those reported by other groups. It could be very useful to clinical and epidemiological purposes, as well as to transcultural studies.