Lead zirconate titanate (PZT) fibres with diameters between 70 and 300 μm have been extruded and sintered at 1200°C in a PbO-enriched atmosphere. Subsequently, the influence of fibre diameter on the microstructure (porosity and grain size) was investigated. The measurements revealed that with decreasing fibre diameter, the porosity decreases whereas the grain size increases. The influence of these microstructural differences on the piezoelectric properties was evaluated using a novel characterisation procedure for single PZT fibres. Fibres with an as-extruded diameter of 100 μm developed an average maximum strain of 3800 ppm at an applied electrical field of 3 kV/mm and exhibited the best performance for all fibres processed with the chosen sintering parameters.