Recent studies have shown that infection with herpes simplex virus type 1 (HSV-1) strain 17 generates in addition to virions a novel type of non-infectious particle. These particles, termed L particles, lack capsids and viral DNA, and consist predominantly of tegument and envelope proteins. We show that L particle production is not restricted to one strain of HSV-1, and that pseudorabies virus and equine herpesvirus type 1 also release particles which are similar in composition to and morphologically indistinguishable from HSV-1 L particles. Data obtained from monoclonal antibody analysis revealed that Vmw175, an immediate early HSV-1 polypeptide which had been previously identified as a virion component, is located predominantly in L particles and not in virions. Following removal of the envelope from L particles, the remaining tegument material largely retained its structural integrity, indicating that the structure of the tegument does not depend on the presence of the capsid or envelope.