In this review, complications and unfavorable conditions during and after preanaesthesia, general and local anaesthesia are discussed. The type of actions to be carried out against such unfavorable conditions or in order to minimise the complications, the type of measures to be taken before anaesthesia and operations have been described. In case of a complication, medicines administered immediately and their doses and the means of administration are explained. Furthermore, adverse conditions that can arise from the instruments and the tools that are used or that can be caused by the anaesthesiologist and the personnel are described and the prevention methods for such unfavorable conditions have been emphasized.