In this work, the vibronic spectroscopy of the p-aminophenol-water 1:1 complex is presented. The S-1 vibrational energy levels of the complex were characterized by REMPI spectroscopy up to 2500 cm(-1) above the band origin. The dispersed fluorescence spectra were recorded for the B.O., 6a(0)(1) and I-0(2) excitations to characterize the vibrational levels in the S-0 state of the complex. Stimulated ion depletion spectroscopy was carried out to determine the higher vibrational levels of the ground state all the way up to similar to3075 cm(-1). The structure and the vibrational levels of the AP-W-1 complex were calculated ab initio at the HF level and DFT with B3LYP functional for S-0, and CIS level for S-1 using 6-31G** basis set. The structure of the AP-W-1 complex compared well with the earlier calculations for this case as well as the other ROH-water (R=aromatic group) complexes reported in the literature. However, the redshift in the electronic band origin was almost half of that observed in other cases. A good correlation was shown to exist between the electronic red shifts and the respective pK(a)* values (the pK(a) in the excited state).