Measurement of the CP asymmetry and branching fraction of B0-->rho0K0.

We present a measurement of the branching fraction and time-dependent CP asymmetry of B(0)-->rho0K0. The results are obtained from a data sample of 227x10(6) Upsilon(4S)-->BB decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at Stanford Linear Accelerator Center. From a time-dependent maximum likelihood fit yielding 111+/-19 signal events, we find B(B(0)-->rho0K0)=(4.9+/-0.8+/-0.9)x10(-6), where the first error is statistical and the second systematic. We report the measurement of the CP parameters S(rho)(0)K(0)S=0.20+/-0.52+/-0.24 and C(rho)(0)K(0)S=0.64+/-0.41+/-0.20.