The opinions on the performance characteristics of the mid arm circumference as anthropometric measurement for malnutrition screening are quite contradictory. In this paper we analyze the specificity and sensitivity of the arm tape under different conditions and conclude that the design of the tape characteristics should aim at an instrument which can satisfy specific needs instead of a general purpose one. We also give some measurements for the practical design of the instrument. 1. This investigation has been carried out under the Contract AID/ta-C-1121 and the Fundación para la Educación Superior. 2. Universidad del Valle. 3. Fundación para la Educación Superior. 4. Community Systems Foundation.