Candida albicans is the most common human fungal pathogen. Healthy people may acquire superficial infections of the skin and mucous membranes. However, immunocompromised individuals may acquire fatal systemic infections. This work aimed to study some of the virulence factors of C. albicans. A total of 250 clinical specimens comprising 105 oral and 145 vaginal swabs collected from neonates and leukemic children and vaginally infected women, respectively. From the collected specimens 150 samples yielded six types of yeast isolates. The most frequently isolated yeast, which represented 58 % was C. albicans, while C. famata and C. tropicalis represented 12 % and 11.8 % of the isolates, respectively. C. parapsilosis and C. dubliniensis represented 8.7 % and 6 % of the isolates, respectively. The least frequently isolated yeast was Cryptococcus neoformans and represented 4 % of the isolates. Beside the clinical isolates, five commensal C. albicans isolates were obtained from the buccal cavity of healthy volunteers and were used as control in the study. The yeast isolates were identified to the species level by cultural and morphological characteristics after growth on SDA media, the ability to form germ tubes and the growth on cornmeal Tween 80 agar media. The identification of the isolates was confirmed by API 20C Aux system and by PCR technique using universal and species-specific primers. To study the virulence factors of C. albicans, the clinical and commensal isolates of C. albicans were tested for the production of phospholipase, lipase and esterase enzymes as well as for their adherence to epithelial cells in vitro. The total cell protein (TCP) of yeast and hyphal forms of the selected C. albicans isolates was analyzed by SDS PAGE and the proteins expressed in the two growth forms for both clinical and commensal isolates were compared. All the tested isolates were phospholipase positive. Although, commensal and vaginal isolates were more phospholipase producers (calculated phospholipase = 0.057 ± 0.064 and 0.45 ± 0.17, respectively) than oral isolates 0.39 ± 0.047), however, these differences were statistically non significant (p > 0.05). The screening for lipase activity using tributyrin method revealed that oral isolates showed the largest zone of lipolysis (12.88 ± 1.38 mm) followed by vaginal isolates (11.77 ± 0.96 mm) and finally commensal isolates (9.9 ± 1.08 mm). These differences were statistically significant (p < 0.05), and could correlate with isolate type and hence virulence. Assay of lipase activity and specific activity using olive oil emulsion in liquid media showed that vaginal isolates gave the highest activity (2.38 ± 0.93 U/ml) followed by oral isolates (2 ± 0.85 U/ml) then commensal isolates (1.9 ± 0.274 U/ml), but the differences were statistically non significant. All the tested isolates demonstrated esterase activity. The study of the adherence capacity showed that the vaginal isolates were more adherent (9.53 ± 1.83) than oral (6.69 ± 0.77) and commensal strains (3.39 ± 0.41), and the differences were statistically significant and could correlate with virulence. By comparing the protein expressed in the two growth forms of C. albicans (yeast form and hyphal form). Protein bands of sizes about 120, 115, 70, and 40 KDa were present in hyphal forms but were clearly absent in yeast forms of the tested isolates. At least one of these proteins (70 KDa) may be hsp due to use of high temperature for hyphal induction, while the other protein bands may be virulent protein bands. Moreover, some differences between the proteins expressed in oral, vaginal and commensal isolates were observed. For the yeast forms, vaginal isolate showed two extra protein bands of about 112 and 100 KDa compared with oral and commensal isolates, vaginal and commensal isolates showed protein bands of about 45 and 35 KDa that absent in oral isolates, also oral and vaginal isolates showed protein band of about 30 KDa that did not appear in commensal isolates and finally commensal isolates showed extra protein band of about 26 KDa. The hyphal forms, vaginal and commensal isolates had a protein band of about 32 KDa that was absent in oral isolate, while oral and vaginal isolates showed a protein band of about 28 KDa that was missing in commensal strains. And these differences may be due to variation in the expression of the different virulence factors between these isolates. Furthermore specific advanced techniques are required to determine the identity and relevance of such proteins. In conclusion, the results of this work suggest that the expression of the virulence factors differ according to the site of infection. Adherence and lipase production can be correlated with virulence for vaginal and oral isolates. Vaginal isolates are more adherent and oral isolates are more lipase producers. There are also some differences in protein expression, but more specific and advanced techniques are required to determine the role of such proteins in virulence.