<p>The study was centred in the evaluation and verification of the lethality of the ethyl acetate fractions, obtained out of the ethanolic extracts of mature, rape, and semi mature fruits, using the shell and the pulp of the species guava (Psidium guajava L) and Choba.(Psidium guineense Sw). The valuation was carried out by means of the bioassay in Artemia saline, through which the following process is evidenced: to determine the Lethal concentration 50 (CL50) using the artificial environment to Ph 7- 8, to bubble in order to saturate the solution with oxygen, to control the eggs appearance to 25 •c after 48 hours, to: xepare the mother and working solution at concentrations of 1500, 1000, 500, 100, 10 mg/ml, strychnine positive control at 80, 70, 60, 50 mg/ml, ethanol solvent target to 80 mg/ml. The biological rehearsal was carried out following the methodologies proposed by Gualdr6n, R (1994); Cyted (1995); Martinez, C (1999) and Mclaughlin, J (1997). Proven the lethality of the acetate fractions of the ehatanolic extract of Psidium guajava Land Psidium gui1eense Sw it showed CL50 181.4 and 221 .30 mg/ml respectively, the results were evaluated according to Gautret (2000).</p>