Experiments using water and toluene have been performed to estimate the pressure drop characteristics in a 2 mm diameter 1 m long conduit. The measurements reveal a significant influence of conduit orientation on frictional pressure drop. The frictional gradient is highest for downflow followed by upflow and minimum for horizontal orientation of the test passage. The influence of orientation is more pronounced for slug flow as compared to dispersed, inverted dispersed and annular flow patterns. In order to explain these observations, an in-depth study of the slug flow pattern has been performed using image analysis. The influence of inlet phase velocities on slug characteristics namely length, frequency and velocity of toluene plugs, in-situ toluene fraction and relative slip between the phases has been investigated. The observations reveal that plug length increases with increasing toluene flow rate while its frequency increases with water flow rate. The in-situ toluene fraction increases with increasing toluene and decreasing water flow rate as expected and it is highest for downward liquid-liquid flow as compared to upward or horizontal flow for the same input conditions. This explains the significant influence of orientation on frictional pressure gradient during liquid-liquid slug flow in a 2 mm conduit. (C) 2014 Elsevier B.V. All rights reserved.