Abstract: A device for collecting biological material, in particular bone marrow and especially stem cells, includes an external cannula for guiding an internal sampling cannula. The external cannula has a mantle wall defining an internal lumen and a distal terminal, and a plurality of openings distributed axially and circumferentially in different longitudinal and/or angular positions. The internal sampling cannula has a mantle wall that defines an internal lumen and that can be coaxially inserted inside the external cannula so that the two cannulas are mobile with respect to each other by axial and/or an angular displacement, and further has a plurality of openings that are distributed axially and circumferentially along the lateral wall in different longitudinal and/or angular positions. The holes in the external and internal cannula are distributed to enable a selective sampling in different angular and/or axial positions along the axial extension of the external cannula.