In this work, the flow of immiscible fluids in a PMMA microchannel 300 mu m wide and 600 pm deep was investigated experimentally. Dyed de-ionized water and kerosene were selected as the test fluids. Flow patterns were observed by using a CCD camera and were identified by examining the video images. Flow patterns obtained at the T-junction and in the microchannel are presented. Superficial velocities varied between 9.26 x 10(-4) similar to 1.85 m/s for water and 9.26 x 10(-4) similar to 2.78 m/s for kerosene. The formation mechanism of slug, monodispersed droplet and droplet populations at the T-junction was studied. Weber numbers of water and kerosene, We(KS) and We(WS), were used to predict the flow regime transition and the flow patterns map. The experimental data of volume of dispersed phase were successfully correlated as a function of We(KS), We(WS), and hold-up fraction. Considering the uncertainty associated with experimental quantification of the process, the results are in satisfactory agreement over the wide range of 1.90 x 10(-3) < We(WS) < 30.43 and 5.90 x 10(-6) < We(KS) < 0.13 with average absolute deviation of only 16.18%. (c) 2006 American Institute of Chemical Engineers.