OBJECTIVE To explore the prognostic value of posterior cerebral artery (PCA) laterality in patients with symptomatic middle cerebral artery (MCA) occlusion on standard medical therapy. METHODS Forty consecutive patients with first onset isolated atherosclerotic occlusion in M1 segment of MCA received medication from June 2009 to March 2013. All patients underwent magnetic resonance angiography (MRA) for assessment of PCA laterality. Clinical data and modified Rankin Scale (mRS) at 3 months were compared between PCA positive and negative patients. Retrospective analysis was performed on their clinical and imaging data. RESULTS Among them, 20 patients (50%) showed PCA laterality on MRA and 32 patients (80%) completed a 3-month follow-up. No significant difference existed between PCA laterality positive and negative groups in a favorable outcome of mRS = 0-1 at 3 months (P = 0.433). CONCLUSIONS The presence of PCA laterality showed no prognostic effect on patients with symptomatic MCA occlusion on standard medical therapy.