Background: The General Health Questionnaire (GHQ) is a measure of current mental wellbeing that has been extensively validated with adults. The instrument has also been used with adolescents.Objective: (i) To assess the psychometric properties of the GHQ-12 among school students in grades 7-10; (ii) to validate it against other psychological tests; and (iii) to suggest a threshold score.Method: The survey was conducted in single sex and mixed schools from the state and private system in Perth, Western Australia. The survey contained the GHQ-12 and measures of anxiety, depression, self-esteem, stress, generalized self-efficacy, social desirability and negative affectivity.Results: There were 336 students (female 55%) with an age range of 11-15 years (median 13). The GHQ showed good internal consistency (alpha 0.88). Girls had higher mean GHQ-12 scores than boys (F (1,326) 15.0, p < 0.001) and scores for both genders increased with school grade (F (3,326) 4.2, p < 0.01). Multiple linear regression showed that depression, anxiety, self-esteem and stress were significant independent predictors of GHQ scores. The model accounted for 68% of the variance (adjusted R (2) ). Screening indices were calculated by comparison with a combined depression and/or anxiety category. Threshold scores of 13/14 for males and 18/19 for females appeared optimal. General Health Questionnaire scores were compared with two criterion groups: adolescents in hospital with alcohol or drug (AOD) related problems and those with problems not related to AOD use. Only the former group had significantly higher total scores.Conclusions: The GHQ-12 showed good structural characteristics and was appropriately correlated with other measures of related traits. Overall, the GHQ-12 appears to be a valid index of psychological wellbeing in this population and was considerably shorter than some of the other instruments.