From the analysis of the interstellar HI in the region of Car OB2, it was possible to identify a large structure, presumably related to the association. This structure, immersed in a very complex ambient (it is seen throughout the Sagitario-Carina arm), consists of a shell expanding at 24 km s¯¹, and of a bubble located in the central part. The coincidences in position, velocity and age strengthen the relationship between Car OB2 and this structure , created by the effect of the evolution of its most massive stars on the interstellar medium.Asociación Argentina de Astronomía