PASS is a web-based software tool which is used in the prediction of the biological activity spectrum of biologically active compounds based on their structure. The prediction tool uses the 2D structure of the compounds as the basic input and predicts the activities of even those compounds which are not synthesised and chemically tested yet i.e., only information about their structural formula is available till now. Hence comparing the structure of the input compound with the structures already present in the data base of the software and giving the activity spectrum of the that compound as the output. This makes the prediction of different biological effects of the compound such as pharmacological and toxicological effects of the organic drug molecules at early stages and therefore enabling users to identify potential leads of drugs and reducing development time of drugs in the field of research and development. PASS online is very well accepted by the users for its easy, efficient and time saving qualities, aiding in reduction of failures in the clinical trials and also finding new indications for the old drugs. The pass prediction tool gives the biological activities (including pharmacotherapeutic as well as toxic effects) of the input 2D structure as the result of prediction in the descending order of their probability ratios Pa:Pi (probability to be active : probability to be inactive), hence giving the output list in order of their most useful activities.