Measurements ofK0/K¯0time-dependent asymmetries in pionic and semileptonic decays with the CPLEAR detector enabled a complete determination of CPT violation parameters in the neutral kaon system. A global fit using the Bell-Steinberger relation yielded values for the CPT violation parameter inK0mixingIm(&dgr;)=(2.4±5.0)×10−5andRe(&dgr;)=(2.4±2.8)×10−4,the determination of the latter relying essentially on CPLEAR measurements. In addition, CPT violation parameters in semileptonic decaysRe(y)andRe(x−)could be measured for the first time. From these results, the equality ofK0andK0masses and lifetimes is tested at the10−18&hthinsp;GeVlevel. Assuming CPT conservation in decays, the 90&percent; C.L. limit on|mK0−mK¯0|can be pushed down to5×10−19&hthinsp;GeV.CPT violation amplitudes inI=0andI=2decays into two pions were excluded at the level of10−4of the corresponding CPT conserving decay amplitudes. ©2000 American Institute of Physics.