We present results of a calculation of properties of low-lying collective quadrupole states in odd-even nuclei within the framework of the proton-neutron interacting boson-fermion model.The importance of proton-neutron degrees of freedom in low-lying collective states of nuclei has been emphasized in recent years by the interacting boson model [ 1 ]. In addition to introducing specific proton -neutron effects, such as the occurrence ofK P = 1 + bands in deformed nuclei [2], this model has the advantage that, being closely related to the microscopic shell model, it allows one to make extrapolations and predictions for properties of nuclei hitherto unknown. The next logical step in the direction of a detailed understanding of nuclear properties is that of performing similar proton-neutron calculations for odd-even nuclei. Because of the large number of low-lying states, these calculations present a major challenge. Previous calculations of odd-even nuclei within the framework of the interacting boson model have been done with the version of the model in which no distinction is made between proton and neutron degrees of freedom [3]. In this letter, we present the results of the first systematic calculations performed using the protonneutron interacting boson-fermion model. The corresponding computer program was originally written by Otsuka and Yoshida [4], and applied to the study of 79Rb and 79Kr in ref. [5]. The calculations presented in this article are based on an improved version of this program obtained by one of us (R.B.), together with B. Visscher [6]. The improvement consists of a prediagonalization and truncation of the boson spectrum before coupling the odd fermion.In the interacting boson-fermion model, spectra of odd-even nuclei are calculated by coupling the collective degrees of freedom, described by bosons, to the single-particle degrees of freedom (fermions). The hamiltonian is written aswhere H (B) is the proton-neutron interacting boson hamiltonian [ 1 ], H (F) is the hamiltonian describing the single-particles degrees of freedom, and V(BF) is their interaction. The structure of the boson-fermion interaction is, in general, rather complex since the bosons are composite rather than fundamental particles and thus one needs to take into account the effects of the Pauli principle. A purely phenomenological treatment of this interaction is not possible, since it contains a large number of parameters. One must therefore rely on a microscopic derivation. Several of these have been given [7][8][9][10]. In the calculations pre-141