In this study, a new optical measurement technique, the PIDV, was described and application of this technique to unsteady flows through a branching pipe was presented. The branching pipe was made of plexiglass and a small reciprocating pump which is speed controlled was used to ensure unsteadiness. Transparent oil was used as working fluid. In the experiments, a pulsed Ruby laser was used a light source to illuminate the flow plane to be analyzed. Double exposured pictures of the illuminated flow area were taken by a motorized photocamera. In the processing of the double exposured pictures a small He-Ne laser was used for point by point interrogation of the film to extract the velocity information. The results obtained in this way were presented and the difficulties encountered were discussed. The results show that the PIDV is a suitable technique for instantaneous 2-D velocity information even for unsteady complex flows.