Hydrothermally synthesized barium titanate (BaTiO3) powders with a submicrometre particle size have been fast-sintered with a heating rate of similar to 200 degrees C min(-1) at various temperatures (1250-1350 degrees C) for short times (5 and 15 min). The microstructures and dielectric properties of the sintered samples are studied and compared with those sintered conventionally. The sample fast-sintered at 1250 degrees C for 5 min had the highest dielectric constant value of approximately 3700 with an average grain size of about 1 mu m. Both the dielectric constant and the Curie-Weiss temperature are found to be dependent on the grain size of the sintered samples, particularly when the average grain size is less than 5 mu m. This has been attributed to the presence of internal stress in the fine-grained BaTiO3.