Solvolytic reactions could be greatly influenced by the presence of neighbouring groups. The tool of increasing electron demand has been successfully used to detect such participation. For example, the tool has detected the presence of major π-participation in anti-7-norbornenyl and π-conjugation in cyclohexen-2-yl derivatives. The changes observed in the absolute values of p + with ring size in cyclic systems could be adequately explained by the I-strain concept. The tool has established major πδ-conjugation in cyclopropylcarbinyl and nortricyclyl derivatives. πδ-participation in the Coates’ cation has been unambiguously established. However, this sensitive probe has failed to provide evidence for δ-participation in the solvolysis of 2-norbornyl system. It, is concluded that the tool of increasing electron demand is quite sensitive to detect the presence or absence or neighbouring group participation. © 1981 Indian Academy of Sciences.