The deuterium quadrupole hyperfine structure of (\left(\mathrm{D}{2} \mathrm{O}\right){2}), a nonrigid dimer displaying four large-amplitude motions, is investigated both experimentally and theoretically. Five hyperfine patterns, corresponding to the (1_{01} \leftarrow 0_{00}) transition, but involving different, nondegenerate as well as doubly degenerate, tunneling sublevels, are recorded under high resolution using a molecular beam microwave Fourier transform (MB-MWFT) spectrometer. These patterns are analyzed using the theoretical formalism developed to calculate the hyperfine energy levels of the analogous (\left(C_{2} D_{2}\right)_{2}) species, presented in a previous paper. This formalism makes it possible to account for the frequency of the hyperfine components satisfactorily. Separate analyses and a global analysis of the five hyperfine patterns are carried out. The second analysis leads to the determination of some components of two effective quadrupole-coupling tensors which, in the theoretical formalism. are needed to calculate the hyperfine energy levels. Using the value obtained for these components. a structural calculation is carried out. (c 1993 Academic Press, Inc.