Research on the influence of sex steroids: ß-estradiol, testosterone and corticosteroids: cortisone, cortisole (glucocorticoids), 11-deoxycorticosterone (mineralocorticoid) and prednisolone (chemical derivative of hydrocortisone) on changes of soluble proteins, nucleic acids and reducing sugars as a content of Wolffia arrhiza ( Lemnaceae ) has been conducted. Wolffia has been cultivated in Bialystok’s municipal tap water (rich in mineral but poor in organic components) during a 20-day period, in the optimal concentration of 10^-5 to 10^-6 M. It has been ascertained that the maximal stimulation of nucleic acids (DNA & RNA) was caused by ß-estradiol in the range from 176-181%, testosterone 168-173%, cortisone 154-157%, 11-deoxycorticosterone 152-155%, cortisole 141-148% and prednisolone from 129-131%, in comparison to a 100% control. The soluble proteins content was stimulated the strongest by ß-estradiol - 181%, testosterone - 170%, cortisole - 141%, cortisone - 138%, prednisolone - 137%, and weaker by 11-deoxycorticosterone - 128%. Reducing sugars content was stimulated most intensely only on the 5^th day of cultivation by cortisone in 165%, 11-deoxycorticosterone - 160-164%, cortisole in 157% and prednisolone in 149%, whereas ß-estradiol had a stimulatory influence of 133-138% and testosterone – 119-121% in comparison to 100% control during the whole period of 20 days of Wolffia arrhiza cultivation.