In this study, twenty five samples ofwell-known herbs in Riyadh, Saudi Arabia were collected and analyzed for Total Fungi Count (TFC). Mycotoxins were extracted and screened using SMKY liquid medium. One hundred and thirty adult female albino mice were grouped into three wherein one group (n = 110) was fed with an aqueous extract from herbal plants. The second group (n = 15) was fed with an aqueous extract of the isolated fungal species. The third group comprised the control group which was given water only (n = 5). All mice were fed with mice breeding diet by Pillsbury, UK. After 5 weeks, mice were fasted and blood was withdrawn for biochemical analysis including alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma glutamyltransferase (GGT), serum creatinine and urea. Calligonum comosum with 2 x 10(5) cfu g(-1) fungus spore, grained mixed herbs (24 x 10(3) cfu g(-1)) and Salvia officinalis (23 x 10(3) cfu g(-1)) were the most contaminated samples. The genus Aspergillus was the most dominant genus recovered (142 isolates) followed by Penicillium (14 isolates) and these two genera were found in 85.0 and 11.0% of the samples analyzed. Aspergillus fumigatus, Aspergillus flavus and Aspergillus ochraceus were the most dominant and frequently isolated (47.3, 46.5 and 18.1%, respectively), followed by Aspergillus citrinum (11.0%). Aspergillus ochraceus had 21.7 microg kg(-1) of Aflatoxin B2 and 7.25 microg kg(-1) of ochratoxin A, whereas Aspergillus flavus had 7.45 microg kg(-1) of Aflatoxin B2 and Aspergillus fumigatus had 3.5 microg kg(-1) of Aflatoxin B2 and 3.8 microg kg(-1) of ochratoxin A. Mean creatinine, urea, ALT, AST and GGT were higher in mice fed or treated with herbal and fungal extracts group than the control group. This study confirms previous studies demonstrating the predominance of Aspergillus species in herbal and medicinal plants and its capability in the production of aflatoxin with induction of nephrotoxicity and hepatoxicity in animals and even in humans.