Abstract The physics objectives other than tests of CP and CPT of a phi factory are discussed. They include: (1) better measurements of the down-up quark mass difference using ϱ° − ω and π° − η mixing studies; (2) the detailed investigation of the validity of the OZI rule and of the quark structure of the φ meson via e +e − → π + π −, π 2 γ, and 3 π measurements; (3) the extraction of important information on the structure of the 0 ++ meson which can be learned from measurements of radiative decays, in particular of φ → ππγ and φ → K Kγ . A phi factory is really a factory of tagged, monochromatic K 5 and K L mesons allowing precision measurements of various neutral K-decay modes. This enables one to make a precision measurement of the V us element of the K-M matrix based on K μ3 ° decay and to perform critical tests of chiral perturbation theory, in particular through the acurate determination of the K π3 , K μ3 , and K → π° γγ decay spectra. Also of interest are the ππ lengths which are obtained from K μ4 decays.