Pb(Zr,Ti)03 thin films with compositions close to the morphotropic phase boundary deposited onto electroded Si substrates have potential for use in ferroelectric memories, sensors and micromechanical devices. The microstructures of such films prepared by in-situ reactive sputtering have been characterised using transmission electron microscopy. (001) oriented films, which were essentially free from second phases, could be prepared by using Ti-rich seed layers. The interfaces between the seed layers and the bulk of the film were sharp with little interdiffusion. The compositional changes across the interfaces often resulted in the formation of subgrain boundaries in the upper layer. In contrast to sputtered films, sol-gel, deposited thin films contained traces of residual pyrochlore at the film/top electrode interface which was considered to impair their switching characteristics. The domain structures of the films were complex with an average domain width of about 20 nm, an order of magnitude smaller than that observed in bulk PZT.