Aims: The pressure responses of four genotypes of F-specific RNA bacterio-phages, f2, GA, Q beta and SP, were evaluated with respect to pressure magnitude, treatment temperature and suspending medium. Method and Results: The pressure responses were studied with respect to pressure magnitude (350 to 600 MPa), treatment temperature (-10 to 50 degrees C) and suspending media. Phages f2 and GA had much higher pressure resistances than Q beta and SP. Pressure resistances of Q beta and SP were enhanced with increase in salt concentrations in the range of 350 to 600 MPa from -10 to 50 degrees C in PBS. Q beta and SP had greater pressure resistances when suspended in phosphate-buffered saline (PBS) with added glucose (5%, w/w), UHT whole milk and Dulbecco's Modified Eagle's Medium plus 10% fetal bovine sera than they did in PBS. Two surfactants, sucrose laurate and monolaurin, and one chelating agent, ethylenediamine tetraacetic acid (EDTA), increased the pressure resistance of Q beta and SP, but had modest effect on either f2 or GA. Conclusions: Four representative F-specific RNA bacteriophages, f2 (serotype I), GA (serotype II), Q beta (serotype III) and SP (serotype IV) showed different resistances to hydrostatic pressure in the range of 350-600 MPa. Significance and Impact of the Study: This study screened for practical surrogates of HAV for validation of commercial high hydrostatic pressure processing.