Introduction:
Life expectancy is the number of years that people in a given country or population can expect to live. Dramatic gains in life expectancy have been made globally since 2000, but major inequalities persist within and among countries of different human development.

Aim of the research:
To identify determinants of life expectancy in countries that have low and medium human development index.

Material and methods:
The study was conducted from January 1, 2018 to April 15, 2018 using the most recent aggregates of health indicator data from the WHO, World Bank, UNDP, and UNICEF databases in 83 countries with low and medium human development. The dependent variable was life expectancy, while the independent variable was socio-economic, healthcare related, and morbidity variables. Data was compiled in excel and analysed using SPSS version 21. A linear relationship was drawn between variables and presented in tables.

Results:
Life expectancy was shorter in the studied countries and varied enormously among countries. A significant relationship between life expectancy and socio-economic, healthcare, and morbidity indicator variables was observed. There was an inverse and significant linear relationship between life expectancy and young age dependency rate, total fertility rate, child mortality rate, and a positive relation with HDI, adult literacy rate, contraceptive prevalence rate, HIV incidence rate, and TB incidence rate.

Conclusions:
Life expectancy is determined by multiples of socio-economic factors, health and health care system associated factors, disease burden, and their complex interactions. Therefore, policy and programs targeted to improve life expectancy should consider population dynamics, socio-economic influence, and health system factors.