We studied the activity levels of matrix metalloproteinase 1, 2, and 9 in periovulatoryf luids from naturally occurring menstrual cycles versus those from samples taken from menstrual cycles stimulated with clomiphene citrate or recombinant stimulating hormone. No statistically significant differences were found. We studied the activity levels of matrix metalloproteinase 1, 2, and 9 in periovulatory f luids from naturally occurring menstrual cycles versus those from samples taken from menstrual cycles stimulated with clomiphene citrate or recombinant stimulating hormone.