The dependence of the shape and size distribution of aggregates of lead zirconate titanate nanoparticles prepared by spray pyrolysis of a sol-gel precursor solution is reported. Decreasing the average heating rate from 300 to 160 degrees C s(-1) in the sub-200 degrees C section of the reactor decreased the proportion of non-spherical particle aggregates and decreased the maximum size from similar to 10 to similar to 5 mu m. Microtome sectioning revealed an internal structure composed of < 100 nm primary particles. Both solid and hollow particle aggregates were present.