A species ofArthrobacterwas recovered during culture of the causal organism of pitch canker of southern pines,Fusarium moniliformevar.subglutinans(FMS).Arthrobacteris a relatively common soil bacterium and is lytic to several fungal pathogens in the soil. Soil samples from two seed orchards with pitch canker and one from a healthy pine plantation all yieldedArthrobacter. These isolates were evaluated for their ability to inhibit the growth of FMS isolates from pitch canker tissue and from soil in areas with high pitch canker disease incidence, and to several other species ofFusariumisolated from the same soil samples whereArthrobacterwas recovered. Generally the pitch canker isolates were more sensitive toArthrobacterthan the soil fusaria. There was variation in the ability of theArthrobacterisolates to inhibit the growth of the fusaria recovered from the soil at the three different test sites. Light and scanning electron microscope observations revealed that hyphae of FMS growing near an isolate ofArthrobacterwere enlarged, producing many vesicularlike structures. The surface of these hyphae was warped and wrinkled in comparison with normal hyphae.