A study of the first excited states of some members of the beryllium isoelectronic series is performed. An explicitly correlated wave function is used to describe the different bound states. It consists of a correlation Jastrow factor and a configuration interaction model wave function calculated from a generalization of the optimized effective potential method to deal with multiconfiguration wave functions. Accurate values for the binding energy of the different states are obtained. Several other properties are also calculated and discussed. A systematic analysis of the Hund's rules through the isoelectronic series in terms of the one- and two-body radial densities and some of their radial moments is carried out. The optimization of the wave function and the calculation of the different quantities is carried out by means of the variational Monte Carlo method. (C) 2003 American Institute of Physics.