Hi Karen, You have the variable order wrong in your call. According to the 5.22 users guide it should be rho_un( salt, temp, p) When you use it like this , and with pressure in dbars (meters approx) you can replicate exactly the values in table a3.1 of Gill's book Atmosphere Dynamics e.g. list/form=(f10.3) rho_un(35, -2, 1000) -> 1032.958 the value for 35PSU, -2degC at 1000dbar = 100bar. Mick Spillane