Photography of tiny oil drop tracers carried by air flowing in a rectangular pipe has been used to measure the fluid velocity at various distances from the wall. Measuring accuracy of better than±0.5% over most of the profile yields agreement with the predicted parabolic profile. The measurements are carried out in an all‐glass section of pipe of cross section 9.5 × 102 mm; the pipe flow Reynolds number is 15, and the duration of the measurement is 0.2 sec.