To assess referrals from primary care practitioners to an ophthalmological practice in order to determine whether any differences exist between the two primary care groups in the types of conditions referred, and in concurrence between reasons for referral and ophthalmological diagnosis. This study investigated patient referrals from general practitioners and optometrists to an ophthalmologist's practice in Belfast, over a period of 3 months from January 2007 to the end of March 2007. Anonymised data were divided into two groups depending on the referring practitioner. Within the two groups, patient numbers were sub-divided into 15 categories covering the range of diagnoses made. Preliminary diagnoses or reasons for referral were compared with the definitive diagnoses made by the ophthalmologist. Optometrists contributed the greatest number of referrals (323) with 243 patients referred by general practitioners. Cataract was the most common condition referred by optometrists, and the second most common condition referred by general practitioners: agreement with ophthalmological diagnosis was high for both groups of primary care practitioners. Concurrence of referral reason with ophthalmological diagnosis for glaucoma was lower for general practitioners (56%) than for optometrists (76%), but optometrists referred more false positive patients for glaucoma than did general practitioners. The opposite was true for lid/tear duct/conjunctival conditions, the most common basis for referral by general practitioners. The differences between the two primary care practitioner groups may reflect variations in training, skills and practice. Further investigation of the particular strengths of both groups, and how they can be optimised to promote effective shared care, is required.