Abstract Surface mud logging systems have detected a severe form of torsional vibration that causes rapid destruction of polycrystalline diamond compact (PDC) drill bits. These failures can occur when combining a limber bottomhole assembly (BHA) with a PDC bit lacking some form of anti-whirl stabilisation. On the basis of experience to date, these vibration-induced failures occur only in larger hole sizes. This paper describes the nature of these bit failures, their dependence on operating conditions, and practical recommendations for avoiding failure. Experience from one operation, in which revised drilling practices and bit selection criteria eradicated the failures, will be presented.