The use of liquid-liquid slug flow in the capillary microreactor is a promising technique for intensifying heat and mass transfer in liquid-liquid reactions. Although the concept has so far been exploited without much reference to the detailed hydrodynamics involved, these are nevertheless inherently crucial to its potential for providing well-defined reaction conditions and identifying asymptotic performance limits and thus a worthwhile subject for more rigorous analysis. In this work, the effect of various operating conditions on the slug size and pressure drop has been investigated. Experiments were carried out to determine these parameters using a Y-shaped mixing element with various downstream capillaries. The experimentally measured pressure drops are in reasonably good agreement with the theoretically predicted values. The capillary dimensions exhibit a significant effect on slug size and pressure drop.