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Experiments are described in which flow stress, electrical resistivity and dislocation density were measured as functions of tensile plastic strain in 99·996% polycrystalline copper extended up to 10%. Dislocation density was measured by the technique of thin film electron microscopy. An apparent anomaly in the results involving dislocation density measurements is interpreted as being due to dislocation loss during thinning. This appears to have increased rapidly with dislocation density above a critical dislocation density.

Flow stress, electrical resistivity and dislocation density were measured in lightly cold-worked polycrystalline copper of 99·996% purity. Dislocation density was measured by thin film transmission electron microscopy. The dislocation resistivity was found to be independent of the dislocation density and to have values(l·3±0·l) × 10-19ohm cm3 at 4·2°k and (1·6± 0·1) × lO-19 ohm cm3 at 77°K.

Flow stress, electrical resistivity changes and dislocation density were measured in lightly cold-worked and in partially annealed polycrystalline aluminium of 99·996% purity. Dislocation density was determined by thin film transmission electron microscopy. The dislocation resistivity obtained from these measurements was found to be independent of dislocation density and arrangement, and to have values (2·9 ± 0·4) × 10-19 ohm cm3 at liquid air temperature and (1·8 ± 0·1) × 10-19 ohm cm3 at 4·2°K.