Oncologic, chronic and infectious diseases are the most important causes of hospitalization. However, there is little data on their frequency and time trend. Therefore, the aim of this study was to determine the epidemiological characteristics and trend of oncologic, chronic and infectious diseases in a public hospital in Lima. An analytical cross-sectional study was carried out. The minimum sample size was calculated at 1225 patients; the data were taken from the data collection forms of the Peruvian Ministry of Health. The main variables were the most common diseases of the groups: oncologic, infectious and chronic, taking into account their final ICD-10 classification. Of the 5086 patients, the median age was 57, with an interquartile range of 42-70 years; chronic diseases were the most frequent (39%) and have a stationary temporal trend, followed by oncological diseases with a tendency to increase, the least frequent were infectious diseases and with a tendency to decrease. In conclusion, chronic diseases were the most frequent, with a stationary temporal trend over time, oncologic diseases were the second most frequent, with an increasing trend over time, and infectious diseases were the least frequent, with a tendency to decrease over time.