The phenotypic properties of representatives of the five genetic classes of pleiotropic-negative sporulation mutants have been investigated. Protease production, alkaline and neutral proteases, was curtailed in spoA mutants, but the remainder of mutant classes produced both proteases, albeit at reduced levels. The spoA and spoB mutants plaqued phi2 and phi15 at high efficiency, but the efficiency of plating of these phages on spoE, spoF, and spoH mutants was drastically reduced. Antibiotic was produced by the spoH mutants and to a degree by some spoF mutants, but the other classes did not produce detectable activity. The spoA mutants were less responsive to catabolite repression of histidase synthesis by glucose than was the wild type. Severe catabolite repression could be induced in spoA mutants by amino acid limitation, suggesting that the relaxation of catabolite repression observed is not due to a defect in the mechanism of catabolite repression. Although others have shown a perturbation in cytochrome regulation in spoA and spoB mutants, the primary dehydrogenases, succinate dehydrogenase and reduced nicotinamide adenine dinucleotide dehydrogenase, leading to these cytochromes are unimpaired in all mutant classes. A comparison of the structural components of cell walls and membranes of spoA and the wild type is made. The pleiotropic phenotypes of these mutants are discussed.