Abstract: A new alarm system for pulse oximeters, based on fuzzy logic, will differentiate false alarms, caused by artifact, from true alarms. Numeric input variables and corresponding fuzzy sets (oxygen saturation HIGH (high O2), NO (normal O2) and YES (desaturation) and rate of change of oxygen saturation (HIGH, MEDIUM and LOW) and their membership functions are defined. An output fuzzy set ARTIFACT is defined. Input voltages from the pulse oximeter are sampled and converted to digital form. The sampled voltages are converted by the membership functions into confidences that each fuzzy set descriptor for oxygen desaturation and reate of change apply. Rules are specified which result in confidences that the fuzzy set descriptors for ARTIFACT apply. Further rules govern the issuance of alarms for oxygen desaturation or for artifacts, momentary or continuous, so that the nurse can take appropriate action. The fuzzy logic alarm system program is written in Quick Basic 4.5, by Microsoft (R).