Thls paper Presents the f lrst verslon of GENES IS, an expert system shell sultable for the development of alarm pattern recogn It Ion expert systems (APRES). GENES IS Includes a series of algorlthms and procedures especially deslgned for a rapld and systematic construct Ion of APRES . The Inputs required by GENESIS are the fault trees of the system under analys Is, the probab I I lty of occurrence of each fault In the trees, and the set of symptoms (alarms and measurements) associated to the occurrence of each Individual fault.Wlth thls lnformat Ion, GENESIS generates a set of productlon rules which relates faults and symptoms. The shell uses these rules and the probability of occurence of each of the faults In order to generate opt lmal alarm pattern recognltlon strategles (algorithm of the Inference engine). A strategy helps the operator to recognize which alarm pattern Is occurrlng wlthout havlng to search the entlre set of patterns. Al I the alarm pattern recognltlon strategtes are generated off-line, as a consequence, the response of the system WI I I be very fast. Thls feature makes GENESIS a powerful tool for the da% lopment of rea l-t I me APRES.