The free jet millimeter wave absorption spectra of the 1:1 complexes between two isotopomers of pyrrolidine (normal and N-D) and four isotopomers of water (H2O, HOD, D2O, and (H2O)-O-18) have been assigned. Although only the rotational spectrum of axial-pyrrolidine has been previously reported, the adduct is formed with equatorial-pyrrolidine. The water molecule lies in the plane of symmetry of pyrrolidine; the water hydrogen involved in the hydrogen bond is axial with respect to the ring, while the "free" hydrogen is entgegen to the ring. The three atoms involved in the hydrogen bond adopt a bent arrangement with a N-ring... H distance of about 1.89 Angstrom and angle(N-ring... H-O) congruent to 163 degrees.