Background: ChileanAIDS Cohort is the oldest and extensive in LatinAmerica and one of most numerous and with longer follow up time to international level. Records information from 14,873 patients out of approximately 22,000 in antiretroviral therapy in the public system and its results have allowed to know the national reality and have contributed to the adoption of public policies. Aim: To describe the demographic, clinical and immunological characteristics of patients who have started ART in Chile and its evolution over the past 15 years. Patients and Methods: The cases were stratified by five-year periods: 2001-2005, 2006-2010 and 2011-2015. The data analysis included calculating proportions, their respective confidence intervals 95% and chi(2)test for significance analysis was applied. Results: 17.4% of patients starting ART are women and the proportion has remained relatively constant. The highest proportion of new HIV cases are 30 and 39 years old, nevertheless the layer of 15-29 years demonstrates a significant increase from 21.7 to 36.4% in 2011-2015 especially in men. 12.1% of new cases are older than 50 years old with a stable trend over time; however, women over 50 have increased from 11.0 to 15.6%. Antiretroviral therapy initiation with CD4+ T lymphocytes less than 200 cells/mm(3) has decreased from 79.7 to 42.4% and in stage C from 45.4 to 22.6%. Late presentation to antiretroviral therapy is higher in men but this gap has narrowed in the last five years. Pneumocystisjiroveci, wasting syndrome, tuberculosis, Kaposi's sarcoma and esophageal candidiasis are the most common opportunistic diseases without significant changes in the three-year periods analyzed. In the last five years, 15.5% of opportunistic diseases occurs in patients with CD4+ TL > 200 cells/mm(3). Discussion: Despite the limitations of observational studies present report describes the characteristics and evolution of the epidemics in Chile in the last 15 years. The infection occurs at younger ages in men, whereas in women there is an increase over 50 years old. Despite advances in treatment access have reduced late presentation to therapy, important challenges remain to achieve more timely initiation of antiretroviral therapy in accordance with WHO 90-90-90 goals.