Introduction: The menstrual cycle is unique to female human beings and a few nonhuman primates. It results from a complex interaction between the hypothalamus, anterior pituitary gland, ovaries and uterus.(1)The average menstrual cycle is of about 28 days (23-29days) and is divided into three phases- proliferative phase, secretory phase, menstrual phase. Thus the cyclic hormonal changes occurred during various phases of menstrual cycle, can affect a variety of physiological and biochemical processes affecting the levels of various minerals like calcium, magnesium and phosphorus present in the body. Aims: The purpose of this study is to evaluate the changes in serum Calcium, Magnesium and Phosphorus levels during various phases of menstrual cycle in healthy normally menstruating female. Materials and Methods: The 100 healthy female volunteers from M.B.B.S students participated as subjects in this study. Each subject has been explained about the procedure of the test to eliminate fear and apprehension. Informed Consent was taken from each subject. The subjects were selected on the basis of normal and regular menstrual cycle i.e (28+4) cycle. Those students having irregular menstrual cycle, distressing symptoms like severe abdominal pain, heavy or scanty menstrual blood loss are excluded from the study. The regular menstrual cycle of 28 days can be divided in to three phases. The blood sample was collected three times from each subject during their menstrual, proliferative and secretory phase. The blood sample was drawn in the morning hours between 8.00 a.m. to 9.00 a.m. during each phase of menstrual cycle. Estimation of serum calcium, magnesium and phosphorus was carried out on the same day of collection of blood sample. Results: In the present study, we observed gradual increase in serum calcium level from menstrual to proliferative phase and gradual decrease from proliferative to secretory phase. Highest level of serum calcium was seen in proliferative phase. It further showed gradual decrease in serum magnesium level from menstrual to proliferative phase and then gradual increase from proliferative to secretory phase. Highest level of serum magnesium was seen in secretory phase. Study showed gradual decrease in serum phosphorus level from menstrual to proliferative phase and also from proliferative to secretory phase. Highest level of serum phosphorus was seen in menstrual phase. Conclusions: Cyclic changes of serum calcium, magnesium and phosphorus are brought under the influence of ovarian hormones acting directly or indirectly. While interpreting the levels of serum calcium, magnesium and phosphorus for any reason, cyclic changes of serum calcium, magnesium and phosphorus were noted during different phases of menstrual cycle.