The flashover of insulator strings occurring at normal working voltages under contaminated/polluted conditions, obviously deserves serious consideration. Though much research has been gone into pollution-induced flashover phenomena but grey areas still exist in our knowledge. In the present experimental study the breakdown (flashover) voltages across gaps on insulator top surfaces and gaps between sheds (on the underside of an insulator), also the flashover studies on a single unit and a 3-unit insulator strings were carried out. An attempt has been made to correlate the values obtained for all the cases. From the present investigation it was found that resistance measurement of individual units of a polluted 3-unit string before and after flashover indicates that strongly differing resistances could be the cause of flashover of ceramic disc insulator strings.