Background: Zoledronic acid was accepted as a line of management of cases with bone metastasis from solid tumors and cases of multiple myloma. It's generally a safe drug, but sometimes it is associated with toxic effects like flu like symptoms, renal impairment and osteonecrosis of the jaw. Dose interval of giving the treatment varies between short (3-4) weeks and long (12) weeks. Aim: to determine the incidence of skeletal related events (SREs), which includes pain, cord compression or pathological fracture and duration of SREs free survival. Also, to assess the incidence of toxicity between different time intervals of giving the treatment. Methods: This is a retrospective study done on cases of breast and prostate cancer with bone metastasis and cases of multiple myeloma who received zoledronic acid for at least 1.5 years. Cases were divided according to time interval of receiving treatment to 3 groups; group 1 received treatment every 4 weeks, group 2 every 6 to 8 weeks and group 3 every 10 to 12 weeks. Results: after a follow up period ranging between 26 and 36 months, it was noticed that as the time interval of receiving zoledronic acid increased, the number of cases developed SREs increased, with non-significant P value (0.071). Regarding the incidence of toxicity, it decreased as the time interval increased with non-significant P value for flu like symptoms (0.12), nephrotoxicity (0.28) but it was significant regarding development of osteonecrosis of the jaw (0.029). Comparing the SREs free survival, it was better in short time interval with significant P value (0.027). Conclusion: short time interval of giving zoledronic acid is preferred as its associated with significant SREs free survival. Longer time interval is a good option for cases who can't tolerate the toxicity.