HE EFFECT of temperature, pH, UV, petroleum ether (60-80), .......acetone (99 %), ethyl alcohol (95 %) and chloroform (99 %) on the infectivity of local coliphage isolates was studied. Three E.coli phages (ECP) were isolated from Ismailia Canal at Mostorod segment. Ability of local E.coli isolates to serve as a host was evaluated after storage at 4-6ºC, 25-28º C and 35-38º C for six months. E.coli isolate number 1 of seven tested served as host for phage reproduction and plaque formation (PF). Phage isolates were identified by plaque size and electron microscopy. ECP1 and ECP2 are Podoviridae and ECP3 is a Siphoviridae. The infectivity of coliphages decreased with increasing storage periods and incubation temperature. Exposure of somatic coliphages to acidic or alkaline pH, organic solvents or UV radiation (240 nm) or heating (≥ 60º C) diminished infectivity. Ability of E.coli1 to serve as a host for somatic coliphages inversely related to its age. No detectable effect was found for lower temperature ≤ 5º C on the infectivity of coliphage isolates during storage periods.