In many industrial processes, the presence of liquid and gas mixtures creates a slug flow. This kind of regime is observed when slug's liquid blocks the whole pipeline and moves as a coherent mass downstream at a velocity approximately equal to the gas velocity. The aim of this study is to provide statistical information on slug in two-phase flow in horizontal pipe. Experiments were conducted in a pipe of 0.04 m diameter and a length of 14 m. First of all, a flow regime map is compiled for air/water two phase flows. Data on pressure gradient, slug frequency and liquid holdup are presented. It was found that mean slug frequency clearly increases as the superficial liquid velocity increases but it weakly depends on the superficial gas velocity. [ABSTRACT FROM AUTHOR]