A novel method for synthesizing monodisperse 10 nm Lead Sulphide (PbS) nanocrystals in the conducting polymer poly-(3-hexylthiophene-2,5-diyl) (P3HT) at elevated temperatures is reported. Transmission electron microscopy shows that nanocrystals grow rapidly to 10 nm with a monodisperse size distribution. Selected area electron diffraction shows rings that are matched to the PbS rock-salt crystal structure. Steady-state optical spectroscopy and energy dispersive X-ray spectroscopy are also used to confirm the formation of PbS nanocrystals. © 2006 Elsevier B.V. All rights reserved.