The prevalence of hidden psychiatric morbidity was assessed using the General Health Questionnaire (GHQ) and Hospital Anxiety Depression Scale (HAD). A total of 149 Bahraini patients aged > or = 16 years were selected randomly from those attending primary health care centres for problems other than psychiatric illness. The prevalence of psychiatric morbidity using GHQ was 45.1% (cut-off > or = 5) and 27.1% (cut-off > or = 9). Using the HAD scale, the prevalence was 44.4% (cut-off > or = 8) and 23.6% (cut-off > or = 11). Psychiatric morbidity was more common in women aged 50-55 years, in divorcees or widows and in lesser educated patients. Either instrument could be used to diagnose psychiatric illness