The objective of the present study is to investigate the hydraulic characteristics and single-phase thermal behaviour of a capillary tube with internal diameter of 130 µm. As the Reynolds number varies in the range from 100 up to 8000 in the experiments, flow regimes from laminar to turbulent can be thoroughly investigated. In particular, the laminar-to-turbulent transition is studied in depth in order to clarify the discrepancies among different researchers on the transition Reynolds number range. Experiments indicate that in laminar flow regime friction factor is in good agreement with the Hagen-Poiselle theory as far as Reynolds number value is below 583. For higher values of Reynolds number, experimental data depart from the Hagen-Poiselle law to the side of higher λ values. The transition from laminar to turbulent regime occurs for Reynolds number in the range 1881-2479, this transition is in good agreement with the flow transition for rough commercial tubes. Diabatic experiments show that heat transfer correlations in laminar and turbulent regimes developed for conventional tubes are not adequate for calculation of heat transfer coefficient in microtubes.