Abstract : The dislocation microstructures of diopside single crystals deformed at high-pressure (4 <= P <= 9 GPa), high-temperature (1100 degrees <= T <= 1400 degrees C) using a Deformation-DIA high-pressure apparatus (D-DIA) have been characterized by transmission electron microscopy using weak-beam dark-field (WBDF), precession electron diffraction (PED), large-angle convergent-beam electron diffraction (LACBED) and the thickness-fringe method. Dislocation glide is the dominant deformation mechanism under these conditions. The 1/2 < 110 >{1 (1) over bar0} glide is controlled by lattice friction on the edge segments and shows extensive cross-slip. The [001] glide occurs mostly on {110}; no evidence for [001](010) glide has been found. The [100] dislocations bear a strong lattice friction probably due to complex (out of glide) core structures