In spite of tremendous advances in medical science, sleep has not been understood completely. The causes for many of parasomnias are still not evident. Even then these parasomnias are treated with different drugs, one of the major groups among them being sedative hypnotics. The use of sedative hypnotics are always associated with adverse effect, and there is many a times loss of the normal sleep architecture. This causes problems both during drug intake and with the withdrawal of drugs. Hence the need for today is the use of sedative hypnotics with minimum alteration in sleep architecture. The changes in the sleep architecture with the administration of sedative hypnotics can be recorded with the changes in the normal sleep EEG pattern. In this review effort has been made in elaborating the various sleep EEG pattern changes, resulting with the use of different groups of sedative hypnotic drugs with a brief note on their respective mechanism of action and pharmacological properties.