Apical application of silver nitrate (AgNO3; 50 and 100 μg per plant) and silver thiosulphate anionic complex (Ag(S2O3) 2 (3-) ; STS; 25, 50 and 100 μg per plant) to female plants of Cannabis sativa induced the formation of reduced male, intersexual and fully altered male flowers on the newly formed primary lateral branches (PLBs); 10 μg per plant of AgNO3 was ineffective and 150 μg treatment proved inhibitory. A maximum number of fully altered male flowers were formed in response to 100 μg STS. The induced male flowers produced pollen grains that germinated on stigmas and effected seed set. Silver ion applied as STS was more effective than AgNO3 in inducing flowers of altered sex. The induction of male flowers on female plants demonstrated in this work is useful for producing seeds that give rise to only female plants. This technique is also useful for maintaining gynoecious lines.