In the present study we have investigated three-photon ionization inCa in which autoionizing states are engaged. The two-photon resonantprocess (from the Ca ground state 4s2 1S0) occurredthrough or at least in the vicinity of one of the following states:4s4d 1D2, 4p2 3P2, 4s6s 1S0, 4p2 1D2 and 4p2 1S0, with the third photon either reachingthe continuum directly or one of the autoionizing states. The three-photonresonant transitions to 3dmp, mf: 1P1, 3P1 and 3D1 autoionizing states for m up to 21 have beenobserved. Some of the autoionizing resonances which we have found hadnot been observed before in a high-resolution one-photon absorptionexperiment (for J = 1) and in multiphoton experiments (for J = 3). We have compared the ionization signal as a function of thelaser detuning and the laser intensity with theoretical curvesobtained within a simple model (three-level atom + one-mode laserfield). This gives information about the order of magnitude of thethree-photon ionization probability through autoionizing states.