An experimental study is performed to investigate the effects of two arrays-in-line and stag-gered-of cylinders on the mass transfer from a flat surface on which the cylinders are situated. Both arrays have seven rows of short (height-to-diameter ratio of unity) cylinders and identical transverse and longitudinal pitches. The naphthalene sublimation technique, in association with an automated, computer controlled naphthalene surface measurement system gives detailed local mass transfer information. The distributions of local mass transfer coefficient reveal the details of establishment of a periodic regime as well as recurring local maxima and minima. Characteristics of mass transfer from the region immediately adjacent to the base of a cylinder in an array are comparable to that around a single, isolated cylinder. Area-averaged mass transfer results, obtained from numerical integration (summation) of the local data, provide a direct, region-by-region comparison between the two arrays. The arrays produce mass transfer enhancement from the surface of approximately 46 and 53% for the in-line and the staggered arrays, respectively.