Chemistry Department, D. S. College Aligarh-202 001, India Manuscript received 4 August 2003, revised 12 April 2004. accepted 11 June 2004 \(SC_2H_5\) \(\mid\) Two carbamate pesticides namely S-ethyl-N-[(methylcarbamoyl)oxy]thioacetimidatc (a) (CH3-C=NOCONHCH3) and N-phenyl-(ethylcarbamoyl)propyl carbamate (b) [C6H5NH-COO-CH(CH3)-CO-NH-(C3H7)] were synthesized in the laboratory. With the help of elemental analysis. IR and NMR spectra their structures were elucidated. The biological studies showed that S-ethyl-N-[(methylcarbamoyl)oxy]thioacetimidate (a) acts as insecticide against insects causing damages to potato, tomato, cabbage plants, while N-phenyl-(ethylcarbamoyl)propyl carbamate (b) has herbicidal character and can be used for cabbage and legume family crops. For estimation of the toxicity of these pesticides LC50 and LD50 were determined. The results revealed that for fish and rats compound (a) was more toxic than compound (b).