Low-temperature Fischer-Tropsch synthesis was investigated in micro packed-bed reactors. Co/Re/γ-Al2O3 catalysts with different particle shapes and sizes (60 to 580 μm) were employed. Tubular reactor geometry with lengths of up to 1 m was chosen. Pressure drop measurements in the absence of reaction and during reaction were carried out. For analysis of the experimental data a reactor model was developed, which was also used for the determination of liquid holdup. It could be observed that the liquid holdup is independent of conversion, reaction temperature, C5+ productivity, and reaction rate. For irregularly shaped catalyst particles, a liquid holdup in the range of 3 % was observed.