Abstract: Signal defined as an information arising from multiple sources which suggests a new potentially causal association, or a new aspect of a known association between a drug and an event or set of connected events, either adverse or useful, that’s judged to be of adequate probability to justify verifying action. Signals of either adverse or useful effects could arise from literature reports, epidemiological studies, clinical trials, meta-analyses, health Authority safety communications, post-authorization safety studies and spontaneous reports of suspected ADRs. Collections of ICSRs in giant numbers stay the most supply of data and need effective analysis for signal detection. A primary aim in observation of drug safety is that the timely detection of either new adverse drug reactions (ADRs) and beneficial effect or a relevant change of the frequency of both that are already have casual association with an explicit drug, i.e. signal detection. In this article author gives overview on importance of signal detection and various steps involved in signal detection.