The term lacuna or lacunar cavity defines the pathological lesion while the clinical pictures due to lacuna or lacunes are referred to as ‘lacunar syndromes’. The lacunar syndromes include: (1) the typical lacunar syndromes or lacunar syndromes proper - pure motor hemiplegia, pure sensory stroke, ataxic hemiparesis including dysarthria and clumsy hand, sensorimotor stroke and abnormal movement syndromes, (2) reversible ischemic attacks (TIA and/or PTIA or RIND), (3) other clinical syndromes which may be due to lacunar lesions such as suprabulbar palsy; lacunar dementia, or subacute arteriosclerotic encephalopathy (or Binswanger’s disease). The different clinical pictures are reviewed, some mechanisms underlying the lacunar lesion are briefly discussed and the old label ‘small vessel diseases’ in cases with lacunes is rec