Three Candida albicans strains were tested in the presence of 17-beta-estradiol (10-6 M and 10-9 M) for increased growth and for enhanced survival during incubation at nonpermissive temperatures. All 3 test organisms showed increased growth in the presence of estradiol compared with estrogen-free controls. Likewise, all 3 strains, when treated with estradiol, survived incubation at 48 degrees C better than did controls. Cytoplasmic extracts were probed with an anti-hsp90 antibody, and results suggested that intracellular hsp90 was up-regulated in the presence of 10-9 M 17-beta-estradiol. The results were confirmed by reverse-transcriptase polymerase chain reaction with primers specific for C. albicans hsp90. A kinetic study revealed that peak hsp90 expression occurred within 2 h of exposure to 17-beta-estradiol. In addition, estrogen increased the amount of cdr1 (Candida multidrug resistance) mRNA compared with cells not treated with estrogen. Coumarin and phenol also up-regulated hsp90 and cdr1 mRNAs, indicating that the estrogen-sensing and -response systems in C. albicans may lack specificity.