Abstract Strong binding of three scalar quarks is investigated in the framework of Bethe-Salpeter equations. After stating the relevant field-theoretic formulae, possible dynamical assumptions are discussed which can help to describe the observed baryon mass spectrum. Just as in the quark-antiquark case a covariant harmonic oscillator approximation may be formulated, and it is shown that this corresponds to linear Regge trajectories. The resulting Bethe-Salpeter amplitude of the ground state is used in a calculation of the electromagnetic radius by means of the triangle graph model. The oscillator constant as obtained by matching the Regge slope leads, independently of the quark mass, to 0.8 fm for the e.m. radius.