To the Editor: Feder et al. fail to adequately inform readers about the science underlying the "chronicity" debate. Multiple researchers have documented Borrelia burgdorferi's ability to penetrate human cells. In demonstrating the presence of the organism inside neurons and glial cells, Livengood and Gilmore established that it can exist in an intracellular state within a protected site, 1 characteristics favoring persistence and necessitating longer courses of antibiotics. B. burgdorferi's pleomorphic abilities also favor persistence. One study suggested that penicillin, ceftriaxone, and doxycycline are ineffective against the bacteria in its cystic form.2 The study by Yrjänäinen et al. revealed that B. burgdorferi can survive standard therapy, lending further credence to the theory of bacterial persistence.3 Krupp et al. found that, as compared with 23% of the placebo group, had significant improvement in fatigue.4 "Clinical assessment remains the most important method for determining the efficacy of treatment."5 Persistent symptoms in patients with late Lyme disease suggest treatment failure and the need for a new approach. Elizabeth L. Maloney, M.D. 25611 West Comfort Dr. Wyoming, MN 5509