Tom, We routinely use this protocol with excellent reproducibility and results. http://www.nottingham.ac.uk/pathology/protocols/warthin.html Jason D. Burrill Manager, Histology Charles River Laboratories 251 Ballardvale Street Wilmington, MA 01887 ph: 978-658-6000 ext 1652 fax: 978-988-8793 E-mail: jburrill <@t> criver.com