Abstract: For evaluation of 4 Iranian medicinal plant toxicity brine shrimp lethality assays Artemia salina and Artemia uramiana bioassay were used. A. urmiana and A. salina eggs were purchased and kept in a hatching chamber that containing artificial sea water for preparation of nauplii. The active nauplii were collected for study after 48 h. The Plantago major, Artemisia maritime, Mentha piperita and Borago officinalis were prepared in Yasuj, Iran and individually extracted with methanol, hexane and ethyl acetate by Soxhlet apparatus. The toxicity rate of extracts was estimated on the basis of the number of dead nauplii or mortality rate by Artemia salina and Artemia uramiana. LC₅₀ values with 95% confidence intervals were determined by the probit analysis. All extracts, exception of B. officinalis displayed 100% mortality at 1000 μg mL^-1 by A. urmiana and A. salina. Ethyl acetate extract was the most potent and presented the highest percentage of mortality with the lowest LC₅₀ values by both assays too. After ethyl acetate, hexane extract showed the highest toxicity; however the methanol extract exhibited the lowest mortality. According to A. urmiana and A. salina toxicity results, trend of the extracts P. major>A. maritima>M. piperita>B. officinalis was reported. There was a positive correlation between the results from A. urmiana and A. salina, for detecting plants toxicity with a Pearson correlation of R² = 0.989. A. uramiana assay is valuable for the screening of plant extracts to detect of toxicity.