Laminar buoyancy induced flow in a vertical internally finned circular tube has been analyzed by numerically integrating the governing partial differential equations. The temperature of the duct is greater than that of the surrounding fluid; hence the density of the fluid inside the duct is less than that of the fluid on the outside, which creates a hydrostatic pressure head across the duct that induces the flow (chimney effect). Results show that despite reduction in the induced flow rate due to increased friction, a finned tube can yield significant heat transfer enhancement compared to a finless tube of the same height. Depending on the parameters, the degree of enhancement can be comparable to the factor by which the heat transfer area increases due to the presence of the fins.