The The World Health Organization (WHO)Expert Committee on Tuberculosis attempted to formulate prerequisites for reliable sensitivity tests and to specify the technical procedures for them. The first part of the present paper is a joint contribution by the participants in the meeting, summarizing the general conclusions reached and recommendations made with regard to tests of sensitivity to the main antituberculosis drugs-isoniazid, streptomycin and p-aminosalicylic-acid. The other 3 parts descrive, in different tests for determining drug sensitivity the absolute-concentration method, the resistance-ratio method and the proportion method that are generally considered to give reasonably accurate results.