Amaryllidaceae is a well-known family for its high alkaloidal content. These alkaloids comprise a unique group of bases that have been found to occur in this family. The Amaryllidaceae alkaloids represent a large and still expanding group of isoquinoline alkaloids, the majority of which are not known to occur in any other family of plants. This article reports on the phytochemical investigation of the alkaloidal content of the flowers of clivia nobilis cultivated in Egypt which resulted in the isolation of four alkaloids; lycorine with pyrrolo{de}phenanthridine nucleus (lycorine-type) which is the common alkaloid of the amaryllidaceae family, clivatine and nobilisine, both with [2]benzopyrano (3,4-g) indole nucleus (lycorenine-type) and (+) 8-O-demethylmaritidine with 5,10b-ethanophenanthridine nucleus (crinine-type). Furthermore, the antimicrobial activity of the chloroform extract of the flowers of c. nobilis along with some of the isolated alkaloids has been studied.