essential and nonessential metal effects on extracellular leishmania amazonensis in vitro protozoan parasites like leishmania amazonensis are excellent models to test the effects of new drugs against a functional molecular arsenal used to establish successfully an infection in the vertebrate host where they invade the cells of the monocytic system however little is known about the influence of metal ions on the cellular functionality of the infective forms of l amazonensis in the present work we show that zncl2 an essential metal to cellular metabolism did not induce drastic effects on the survival of the promastigote under the conditions tested however incubation of zncl2 prior to subsequent treatment with cdcl2 and hgcl2 led to a drastic toxic effect on parasite survival in vitro nonessential metals such as cdcl2 and hgcl2 promoted a drastic effect on parasite survival progressively with increasing dose and time of exposure notably hgcl2 produced an effective elimination of the parasite in dosestime smaller than the cdcl2 this toxic action induced in the parasite a high condensation of the nuclear heterochromatin besides the absence or destructuring of functional organelles such as glycosomes acidocalcisomes and mitochondria in the cytoplasm our results suggest that promastigotes of l amazonensis are sensitive to the toxic activity of nonessential metals and that this activity increases when parasites are previously exposed to zn to summarize toxic effects of the tested metals are dose and time dependent and can be used as a study model to better understand the functionality of the molecular arsenal responsible for the parasitism