Authors found that in a flow through two intersecting ducts with a 60°intersecting angle, two uneven inlet flow streams may result in an equalization of two downstream exit flows after their collision in the intersecting section and a subsequent formation of vortices in the downstream ducts. It is important to investigate the relation between flows and vortices in intersecting ducts as a basic study. In this paper, an experimental study was conducted to investigate flow characteristics in two intersecting ducts with an extra cavity. Flow visualization by means of a tracer method determined flow patterns, and pressure drop measurements using a piezometer were conducted. It is concluded that flow characteristics included a suction effect in the extra cavity of intersecting ducts are determined by the interaction between vortices and main streams.