The present paper discusses a greenhouse experiment carried out at the Departamento de Solos, Geologia e Fertilizantes da Escola Superior de Agricultura "Luiz de Queiroz" da Universidade de São Paulo, Brazil, to observe the phytotoxic affects on sweet sorghum (Sorghum bicolor L. (Moench) of different doses of biuret added to urea and applied both to soil and leaves. Two types of soils were used - Sandy Quartz and Clayish - Terra Roxa, and the following treatments applied: 1 - 1.15 g N/pot in soil 2- 1.15 g N/pot + 1% biuret in soil 3- 1.15 g N/pot + 2% biuret in soil 4- 1.15 g N/pot + 3% biuret in soil 5- 1.15 g N/pot foliar application 6- 1.15 g N/pot + 1% biuret foliar application 7- 1.15 g N/pot + 2% biuret foliar application 8- 1.15 g N/pot + 3% biuret foliar application The amount of urea applied was 2.5g/pot. The results showed that both soil and foliar biuret applications did not affect the metabolism of the nitrogenous compounds (proteins and aminoacids) although there was variation in sugar content.