Objective: The menstrual cycle represents a continuous state of change in terms of female sex steroid environment. Progesterone is linked to increased fat storage while estrogen exerts anti-lipogenic effects. This study investigated variations in the potent lipogenic factor acylation-stimulating protein (ASP), and examined its association with hormonal and lipid profile alterations across the menstrual cycle. Methods and design: Nineteen non-obese women with regular menstrual cycles were investigated in a longitudinal study during the follicular, ovulatory, and mid-luteal phases (ML) of the cycle. Fasting ASP, LH, FSH, progesterone, estradiol, insulin, lipid profile, and apoproteins were evaluated during different phases of the cycle. Results: ASP levels changed significantly throughout the menstrual cycle (K-related Friedman test: PZ0.013). Interestingly, these changes coincide with variations in progesterone levels across the cycle as no significant change in the ASP levels was seen across the follicular phases of the cycle, followed by a significant increase in the ovulatory phase, which continued to elevate toward the ML. The ASP levels correlated positively with the progesterone levels normally elevated in the ML. No significant correlation was seen between ASP and estrogen or any other measured female hormone. Multiple regression analysis including all measured parameters and body mass index showed that progesterone was the only significant predictor of the ASP levels. Conclusion: Our findings suggest that during the menstrual cycle of normal women, the ASP levels coincidentally fluctuate with the progesterone levels, possibly reflecting cooperation between them in fat storage enhancement.