The correspondents are:
Professor Arien Mack, Dr Richard A Macksey, Dr Donald MacLeod, John Maddox, Scott Makeig, Dr Lee Makowski, Professor Zvonimir B Maksic, Dr Neil Law Malcolm, Dr George Mandler, Dr Marc Mangel, Ann Druyan with cosignatories Lester Grinspoon and Carl Sagan (regarding the legal classification of marihuana), Dr & Mrs P J Marcer, Dr Pedro C Marijuan, John Robert Marlow, Dr Lucia M Vaina (regarding David Marr), Robin Marris, K Martin, Vivien Marx, Dr Pietro Mazzoni, Phillip R McBrayer, Sharon McGrayne, Frederick D McIver, Theodore Melnechuk, Jagdish Mehra, Dr V Orel (regarding journals published by Mendelisum), Dr Frank Meno, Jim Middleton, George L Gabor Miklos, James W Milgram, Abraham Miller, B G Miller, Jonathan Miller, Teri Mendelsohn (The MIT Press), Professor Graeme Mitchison, Dr Merrill M Mitler, Kenichiro Mogi, Juelith Munk, Dr Vernon B Mountcastle, and Professor Jan Murken.