Visualization of the flow of both water and diluted macromolecular polymer solutions through transparent-wall pipes was done in the region of laminar-turbulent transition. Coloured streams were injected into the pipe both in the axis and close to the wall. The now was recorded with the frequency of 1000 Hz using a video camera and next the recording was remade with a computer. Basing on the pictures obtained it was identified that the loss of flow stability did not appear sharply, but it was rather a continuous process developing with the increase in Reynolds number. It was observed that perturbance of the flow started in the central region of pipe and propagated towards the walls with the growth of Reynolds number.