Background
Primary dysmenorrhoea, the most common gynaecologic problem of adolescent females, is commonly treated with nonsteroidal anti‐inflammatory drugs or oral contraceptive pills.

Aim
To compare the effect of zinc sulphate with that of placebo on the control of pain severity and duration in adolescent girls with primary dysmenorrhoea.

Materials and Methods
In a three‐month randomised double‐blind placebo‐controlled clinical trial, 120 adolescent females with primary dysmenorrhoea were randomly divided into two groups of sixty: an intervention group (zinc) and a control group (placebo). Zinc was administered in the form of a capsule containing 50 mg/day zinc sulphate beginning on the first day of menses and continuing until three days prior to the end of menses. Each month, the duration and severity of primary dysmenorrhoea were determined. Severity scoring was performed by using a 0–10 scaling system.

Results
In the first month, the duration of pain was significantly lower in the zinc group compared with the placebo group (P‐value = 0.044), while there was no significant difference in pain severity between the groups (P‐value = 0.497). In the second and third month, pain severity and duration in the zinc group were significantly lower than the placebo group (P‐value <0.001). Conclusion Both pain duration and pain severity were decreased by taking oral zinc. The results of our interventional study suggests that zinc may be used to treat primary dysmenorrhoea in adolescents.