In the present paper, the parametric decay instability of an ion‐Bernstein wave (&ohgr;ci<&ohgr;0≲2&ohgr;ci) into a scattered ion‐Bernstein wave and a low‐frequency wave (either an ion‐acoustic wave or a kinetic‐Alfve´n wave) has been examined. It has been demonstrated that this parametric process may be one of the possible sources of ion heating in tokamaks. In addition to this, the possibility of oscillating two‐stream instability (OTSI) of an ion‐Bernstein wave (&ohgr;ci<&ohgr;0≲2&ohgr;ci) or a cold plasma ion‐Bernstein wave (&ohgr;0≲&ohgr;ci) has also been discussed. The explicit expressions for threshold and convective threshold of the decay processes are given. For OTSI, the expressions for maximum growth rate have also been given explicitly.