Primary care practitioners are expected to diagnose and manage common mental health problems. An effective mental health classification for primary care needs to enable differentiation of normality from disease, clarify interactions between mind and body and offer guidance on treatment or referral. Four current options are considered. SNOMED CT is a structured clinical vocabulary embedded in GP electronic record systems: despite widespread use it lacks clarity on disease status and diagnostic precision. DSM-5 is ambiguous on the borders of disease and normality, and takes a cognitive approach towards somatic diagnoses. The 3rd edition of the International Classification for Primary Care (ICPC-3) emerges from the experience of primary care consultations and includes both patient and physician perspectives. ICD-11 for primary care (PHC) is a work in progress: some elements, such as eating disorders, simplify ICD-11 categorizations; others, such as anxious depression and bodily stress syndrome, differ from ICD-11. While field trials offer rationales for these differences, uncertainties remain about their diagnostic status and about their impact on the ability of primary care and specialist mental health services to integrate. To enable more effective nosology and integration of care, greater convergence is recommended between ICPC-3 and ICD-11 PHC.