The introduction of isoflurane to clinical practice follows the search for a nonflammable, potent inhalation anesthetic which, above all, is chemically stable so as to resist biodegradation or attack by other chemicals. These attributes characterize isoflurane (Table 2). The hoped for freedom from hepatic and renal toxicity and from carcinogenic and mutagenic properties is a reality with this drug. Other favorable characteristics include relatively low solubility in blood in relation to anesthetic dose, lack of arrhythmogenic effect, provision of good muscle relaxation, and the absence of central nervous system excitation. Its moderate pungency detracts slightly from the ease of inhaled induction. Disadvantages include respiratory depression, reduced arterial blood pressure, uterine relaxation, decreased uteroplacental blood flow, and likely ability to trigger malignant hyperpyrexia. The frequency and/or significance of tachycardia and dilation of muscle blood vessels in clinical practice remain to be established. We believe isoflurane is a significant improvement over earlier potent inhalation anesthetics.