Social anxiety is one of the most frequent psychological problems nowadays. Its diagnosis and assessment depend on different measures, particularly interviews and questionnaires. Most of these measures have been developed in English-speaking countries and their adaptation to Spanish-speaking countries has not been very accurate. The goal of this work has been the development of a new questionnaire of social phobia/anxiety using social situations reported by a variety of people during six years. From more than 10000 situations recollected, an initial version of the “Questionnaire of Social Interaction for Adults” (CISO-A) was built with 512 items plus 4 questions on sincerity. The instrument was applied to 1552 subjects from diverse regions and with different studies. The exploratory factorial analysis produced a structure of five clearly defined factors that explained 38.4% of the total variance: a) Embarrassing social situations, b) Interactions with strangers, c) Interactions with the opposite sex, d) Speaking/performing in public, and e) Expression of annoyance, disgust or displeasure. Cronbach alpha was very high for all the factors. Based in the former tests, the second version of the CISO-A was elaborated with 139 items. A new exploratory factorial analysis confirmed the former structure. Further analyses will be necessary to establish the reliability, validity and utility of this new questionnaire of social anxiety.