We have developed two methods to determine the tropospheric path delay for microwaves. One uses a closed form model of the atmosphere in which two parameters are used to describe the decrease in temperature with height and the relation between total pressure and water vapor partial pressure, respectively. The other method uses numerical integration of refractivity profiles, which are computed from temperature and humidity profiles obtained by statistical regression. The two methods have been tested on two sets of observations and compared with simultaneous radio soundings. The best results show an improvement of 10% in one case and 30% in the other compared with a presently used model. Possibilities to improve the statistical model further are discussed.