The size and vertical distribution of drops during horizontal dual continuous oil-water flow were studied experimentally. The investigations were carried out in a 38 mm ID stainless steel test section with water and oil (density 828 kg/m(3) and viscosity 5.5 mPa. s) as test fluids. Drop velocities and sizes were obtained with a dual impedance probe which allowed measurements at different locations in a pipe cross-section. The measurements indicated chord lengths up to 20 mm in some cases. Drop concentration and chord length decreased with increasing distance from the oil-water interface. Also, oil drops were found to be larger than water drops since oil tends to lose its continuity at relatively low volume fractions compared to water. The number density of large drops was found to decrease as the water superficial velocities increased while there was no clear effect of oil superficial velocities on drop size. Water drops were in general faster than the velocity of the upper, oil continuous, layer while oil drops could be either faster or slower than the lower, water continuous, layer. There was no clear effect of the layer velocity on the size of drops dispersed in that layer. Finally, it was found that none of the available correlations on maximum drop size was able to predict the present experimental data. These correlations were developed for drop breakage in a turbulent flow field. (c) 2007 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.