Estradiol-17${\beta}$($E_2$) levels in the blood were estimated according to varying the time and amount of the administration of $Clomid^{(R)}$. $Clomid^{(R)}$ were administered on the 2nd, 3rd and 4th menstrual day corresponding to the recruitment period and on the 5th menstrual day corresponding to the selection period of the ovarian follicles, respectively. And $Clomid^{(R)}$ were administered 50 mg, 100 mg and 150 mg/day, repectively. The effects of the sequential HMG to $E_2$ levels in the blood were also estimated. The results were as following : 1. Blood $E_2$ levels according to the day and amount of administration of $Clomid^{(R)}$ were the highest in the group 3(D $2{\sim}6$, 150 mg/day, with HMG) and the lowest in the group 6(D $5{\sim]9$, 50 mg/day, without HMG). $E_2$ levels showed increasing tendency to 0 day. 2. In the cases of the administration of $Clomid^{(R)}$ during the $2nd{\sim}6th$ menstrual day, $E_2$ levels according to the amount were similar among groups and showed increasing tendency daily. 3. In the cases of administration of $Clomid^{(R)}$ during the $2nd{\sim}6th$ menstrual day, $E_2$ levels according to the sequential HMG independent of the amount of $Clomid^{(R)}$ were higher in the with HMG group than without HMG groups. 4. In the case of the administration of $Clomid^{(R)}$ during the $5th{\sim}9th$ menstrual day, $E_2$ levels according to the amount were the highest in the 100 mg/day group and the lowest in the 50mg/day group. 5. In the cases of administration of $Clomid^{(R)}$ independent of the amount during the 5th${\sim}$9th menstrual day, $E_2$ levels according to the sequential HMG were higher in the with HMG group than without HMG group. 6. $E_2$ levels according to the amount independent of the day of the administration of $Clomid^{(R)}$ were the highest in the 100 mg/day group and 150 mg/day, 50 mg/day group in low sequence. 7. $E_2$ levels according to the sequential HMG independent of the day and amount of the administration of $Clomid^{(R)}$ were higher in the with HMG group than the without HMG group. 8. $E_2$ levels according to the day of the administration of $Clomid^{(R)}$ independent of the amount of $Clomid^{(R)}$ and sequential HMG were the highest in the group D 2${\sim}$6 and the lowest in the group D 5${\sim}$9. According to the above results, there were higher $E_2$ levels in the group with sequential HMG than without HMG. Therefore, the hypothesis, postulated initially by the author, was not verified that sequential HMG would not affect the $E_2$ levels which were related to the process of the selection of the ovarian follicle in the connection with 'FSH window'. Because it may be the stimulation after the selection of later predominant follicle. And the highest level of $E_2$ was estimated in the $Clomid^{(R)}$ 150 mg/day group with sequential HMG on the 2nd${\sim}$6th day, and the higher levels were estimated in the 2nd${\sim}$6th day, 3rd${\sim}$7th day and 4th${\sim}$8th day groups than the 5th${\sim}$9th day group. The lower levels were estimated in the $Clomid^{(R)}$ 50 mg/day group without HMG than 100 mg/day and 150 mg/day on the 5th${\sim}$9th day. Therefore, further study will be needed that combines analyses of the E2 levels in the blood according to the various administration of $Clomid^{(R)}$ with or without sequential HMG and determination of the numbers and size of the ovarian follicles by ultrasonogram.