Rapid-sequence induction (RSI) techniques are designed to reduce the risk of aspiration in cases where risk is high. ISR is often for surgery, particularly under emergency conditions, but is also found in procedures requiring emergency tracheal intubation inside and outside the hospital. ISR techniques have proven safe for reducing the risk of aspiration and providing good conditions for intubation in such situations. The great variety of clinical situations that can be involved means that the combination of drugs to be used should be individualized for each case. In addition to the two objectives of RSI named and the particular nature of a case, the risk of presenting unforeseen difficult intubation is yet another factor affecting choice of drugs. Precisely because of this last factor and the good results obtained with short-acting opiates, great interest has developed in recent years in RSI that does not use neuromuscular blocking agents. However, conclusive data are unavailable. Studies are often difficult to compare because of small differences in the combination of drugs, the dosing of one or more of them, the route of administration, or because the criteria used to define ideal intubation conditions are different.