Background: Studies have shown a high worldwide prevalence of mental disorders in primary care. Many patients present with unexplained physical symptoms rather than psychological complaints, resulting in an excess number of costly clinical investigations. This study investigates the ability of primary care physicians to correctly detect and diagnose somatization and depression in Saudi Arabian patients. Methods: In all 431 primary care patients in Riyadh Saudi Arabia were screened for somatization and depression using the Patient Health Questionnaire (PHQ). Primary care physicians independently assessed these same patients while blinded to the results of the PHQ. Agreement between physician observations and the screening instrument was examined. Results: Using the PHQ as the standard of comparison for measuring the detection rates of Saudi physicians, the agreement between and the PHQ and physician assessments was κ=0.40 for depression (0.45 females, 0.31 males) and κ=0.27 for somatization (0.36 females, 0.12 males). Physicians assessed higher rates of somatization than indicated by the screening instrument and demonstrated poor diagnostic agreement on somatization and depression, particularly for male patients. Conclusions: Saudi primary care physicians have awareness of psychiatric disorders, but their diagnostic skills are poor for somatization and depression. Psychiatric training should be supported in the continuing education of primary care physicians and patients should be encouraged to report psychological complaints to family physicians. A simple screening instrument for identifying mental disorders in developing countries is a valuable tool for assessment in primary care.