Natural convection heat transfer to water contained within five different sized spheres was studied. Pseudosteady-state was maintained by keeping the driving force for convection constant, i.e., the temperature outside the sphere was increased steadily so that the temperature difference between the outside and the center remained constant. Flow visualization was used to determine flow patterns within the spheres. Laminar flow was found to exist below Rayleigh numbers of about 107. The flow patterns along with the position of the circulation centers are presented and compared with recent numerical solutions. The overall heat transfer in the laminar region was fitted by least squares and the following correlation obtained: Nu=0.80Ra0.30