The aim of this randomized controlled trial is to determine effectiveness of only calcium and calcium with magnesium on the pain severity and resting length of students with primary dysmenorrhoea. 80 female eligible students with medium to severe primary dysmenorrhoea (VAS≥5) will be recruited at dormitories of Aras branch of Tabriz University of Medical Sciences, after getting written informed consent. The participants will fill in forms reporting severity of pain and other menstrual symptoms, as well as amount of menstrual bleeding on each day of menstrual cycle during 2 following months and the end of the 2 months give them to the researcher. 60 of the recruited people, who have good cooperation in reporting the symptoms, will be randomized using blocks sized 6 and 9 into 3 groups. One group will get capsule of calcium, the second combination of calcium and magnesium and the third one placebo which are identical in terms of size, colour, ... They will be instructed to use them from 15th day of menstruation cycle till end of following menstrual pain and fill in the similar questionnaire as the 2 previous months. They will be given Mefenamic acid capsules to use during the 4 months study cycles, if needed, but they have to report number of the capsules used. The groups will be compared in terms of mean pain score, symptom severity score, resting time, number of Mefenamic acid used, amount of blood menstruation using Covariance test.