AbstractKemp and Kemp have proposed a scheme of inspection for two types (AandB) of non-conformity. There is serial inspection for typeA, continuing until a sequence ofksuccessiveAs is observed. Thesekitems are discarded, and all previous items (since the last inspection forA) are subject to a Dorfman group-screening inspection procedure forB. We develop formulae for the properties of this scheme, when inspection (for bothAandB) may not be perfect, allowing for both false negatives and false positives. Some numerical values given by the formulae are presented, with a view to assessing the robustness of Kemp and Kemp's scheme.