Anthropologists have long studied the human dentition to describe various aspects of population's way of life. particularly, the interest focused on structural changes of the tooth crown related to the shift to specific dietary patterns and techno-cultural factors, as a consequence of the introduction of agriculture. Still, dental size reduction may also occur in response to biological processes such as migration and genetic isolation. The present study aims at assessing dental size reduction occurring in the anthropologically little known south Florida populations dating back to pre-contact times and understand the biological and cultural causes reflected by such modifications. Three samples have been taken into consideration: Republic Groves (ca 1500 BC), Fort Center (200-600 AD) and Highland Beach (800-1200 ADI. Mesiodistal and buccolingual diameters have been analyzed, as well as the B-L summed sizes for the anterior (I1 to C) and the posterior teeth (P3 to M3; and P3 to M2). Bigger teeth are present in the Republic Groves sample, which could be linked to their hunting-gathering economy, larger teeth being more useful for greater demands of mastication.. On the other hand, tooth dimensions differ very little between the two more recent groups. The reduction observed between Republic Groves and Fort Center may find an explanation in their differing in subsistence patterns and techno-cultural factors. The trend from Republic Groves to Highland Beach can hardly find such similar explanation, since both samples were foragers with a very similar subsistence and cultural activity. In the light of this evidence, specific causes are difficult to assess. Migrations through the Antilles corridor could be at the base of the process, and if clearly demonstrated could account for the major reduction between the more ancient and the later groups.