Abstract: Special arranged experiments were designed for SEM in-situ observation on inclusion behavior in seeded P/M Rene95 superalloy at tension loading stage. Two different size Al₂O₃ inclusion's behavior were followed by continuous loading till to fracture. Observed results show that crack can be easily initiated at the interface of larger inclusion and matrix even at the stress level lower than yield. Crack can be also initiated in the inclusion and then propagated to the matrix. Both mechanics show the harmful effect of inclusions in P/M superalloys.