Finger clubbing is a unique clinical sign and is characterised by a focal bulbous enlargement of the terminal segments of one or more fingers and/or toes. Finger clubbing can also be associated with painful and enlarged joints and periostitis of long tubular bones – in this case it represents a syndrome called hypertrophic osteoarthropathy. Finger clubbing and hypertrophic osteoarthropathy represent different stages of the same syndrome, finger clubbing being the first and hypertrophic osteoarthropathy the advanced stage. This syndrome, manifesting itself either as finger clubbing or hypertrophic osteoarthropathy, can be classified as primary or secondary. Primary hypertrophic osteoarthropathy is a rare genetic disorder with diverse clinical manifestations. Secondary form of the syndrome is more common and is associated with a group of diverse internal illnesses, predominantly pulmonary disorders, followed by cardiovascular and gastrointestinal disorders. Finger clubbing may rarely occur without evidence of the underlying disease as an idiopathic form. Mechanism of finger clubbing is best explained by the »thrombocyte theory«. It is proposed that megakaryocytes and thrombocyte aggregates interact with endothelial vascular cells of the peripheral vascular system, thus stimulating the release of different cytokines, such as vascular endothelial growth factor and others which have an essential role in the pathogenesis of finger clubbing. In the case of malignant diseases, vascular endothelial growth factor can be directly released into the systemic circulation. A new onset of finger clubbing can be an alarming clinical sign and should always be further investigated, as it can be the first manifestation of a severe, otherwise asymptomatic underlying disease. In this way, the time to a diagnosis can be reduced and the prognosis of the underlying disease can be improved.