The exclusion eliminates coverage for claims made against attorneys who are not insureds under lawyers professional liability insurance policies yet who share office premises with attorneys who are insureds under such policies. For example, attorneys A and B share office space yet are not partners; nor do they collaborate on any cases. The exclusion is necessary because attorneys who share office premises with insured lawyers have, in the past, made claims under these insured lawyers' professional liability insurance policies. Such lawyers assert theories such as "apparent partnership" or "apparent" or "ostensible" agency or make the argument that, because they share the same office space, the insured lawyer is vicariously liable for the acts of any lawyers who also occupy the same office premises.