Three flavor neutrino oscillation constraints from accelerator, reactor, atmospheric and solar neutrino experiments

We discuss constraints on three flavor neutrino mixings from the accelerator and reactor experiments, the Kamiokande multi-GeV data, and the solar neutrino observations. The LSND result is excluded at 90\%CL by the constraints imposed by all the data of reactor and accelerator experiments and the Kamiokande multi-GeV data if the mass scale required for the solution to the solar neutrino problem is hierarchically small. The region of a set of the effective two-flavor mixing parameters ($\Delta m^2$, $\sin^22\theta$) is given for the channel $\nu_\mu\rightarrow\nu_e$ which is allowed at 90\%CL by the multi-GeV Kamiokande data alone.