OBJECTIVES:  Poor adherence to medications is associated with reduced treatment benefits. Many patients discontinue oral medications for osteoporosis soon after treatment initiation. Our aim was to describe utilization patterns of osteoporosis therapy including primary non-adherence, early discontinuation, treatment reinitiation and long-term adherence in naïve patients prescribed antiosteoporotics METHODS:  Prospective cohort study comprising men and women ≥50 years (ESOSVAL cohort) who started antiosteoporotic treatment between 2009 and 2011. Data were obtained by linking diverse electronic health records of the Valencia region, which allows the differentiation between prescriptions (what the doctor prescribed) and refills (what the patient fills from the pharmacy) at individual level. A descriptive analysis was performed categorizing patients as primary non-adherent (patients who fail to fill initial prescriptions), early non-persistent (discontinuation within the first 3 months) and persistent. Reinitiation within 12 months and adherence (PDC) at 24 months were estimated RESULTS:  From 712 naïve patients in ESOSVAL cohort, 46 (6.5%) were primary non-adherent, 185 (26.0%) were early non-persistent and 481 (67.5%) were persistent. Among primary non-adherent and early non-persistent patients, 91.3% and 57.3% respectively, had a new prescription after their adherence gap during the first year; of those, 31% and 23.6% did not refill it. Mean PDC at 24 months was similar for primary non-adherent and early non-persistent patients who were prescribed again after their adherence gap (33.3% and 34.8% respectively), and 68.2% for persistent patients. At 24 months, 14.3% of primary non-adherent, 4.7% of early non-persistent and 47.6% of persistent patients were fully adherent (PDC≥80%) CONCLUSIONS:  One third of patients who were prescribed an antiosteoporotic either did not initiate treatment or discontinued therapy right after initiation. Most of primary non-adherent and early non-persistent patients reinitiated therapy within 1 year, however their long-term adherence was very low. For persistent patients, long-term adherence was also suboptimal