Mathematical Methods of Operations Research (I 998) 47:341-353The M/M/c with Critical JobsIvo ADANEindhoven University of Technology, Department of Mathematics and Computing Science,Box 513, 5600 MB Eindhoven, The Netherlandse-mall: iadan@win.tue.nlGERARD Hoo~mEMSTRADelft University of Technology, Department of Mathematics and Informaties, Box 356,2600 AJ Delft, The Netherlandse-mail: g.hooghiemstra@twi.tudelft .nlAbstract: