Adherence measurement of treatments is necessary, in spite there are several tools the most of them do not achieve fully the goal. Adherence is a word that includes two concepts: compliance to doses and administration way and persistence on the treatment time. One of these tools is the pharmacy data base. It has been demonstrated using this tool that persistence for osteoporosis patient treatments could be fewer than 25% after one year of prescription. An extended tool is the count of not taked pills that inform of adherence percentage in a period of time. One very useful self- administrated questionnaire is the Morisky-Green with a Spanish version validated by Val Jimenez et al. This questionnaire consists of four simple and short questions. Recently it has been introduced electronic methods that permit to know when and what time the patient takes the pill. Measurement of adherence is not easy and it is necessary to use some tools at the same time to avoid overestimation. Diseases with a long period of treatment as osteoporosis the increase of adherence is needed to prevent fractures.