The gas hold-up in nitrogen/water Taylor flows in a glass microchannel of rectangular cross-section (100 µm × 50 µm) was shown to follow the Armand correlation. The validity of the Armand correlation implies that the liquid film thickness is not a function of the bubble velocity, which was varied between 0.24 and 7.12 m/s. Images of the Taylor flow were captured at a rate of 10,000 frames per second and were used to obtain the bubble and liquid slug lengths, the bubble velocity, and the number of bubbles formed per unit of time. A mass balance-based model was developed for Taylor flow with negligible liquid film velocities. The model describes the gas hold-up as a function of the liquid film thickness, the bubble and liquid slug lengths, the liquid superficial velocity, and the bubble formation frequency.