This disclosure provides systems, methods and apparatus, including computer programs encoded on computer storage media, for group formation and sounding for distributed multi-user multiple input multiple output (MU-MIMO). Some implementations include a method of wireless communication. The method includes a sounding preparation phase that includes transmitting, to the plurality of access points, a first frame inviting the plurality of access points to perform a beamformed distributed transmission from the plurality of access points to a group of stations; receiving a second frame from at least one of the plurality of access points based on transmitting the first frame, the second frame including at least one identifier of at least one station in a different basic service set than a basic service set of the first access point; and identifying the group of stations based on the at least one identifier included in the second frame.