Russian standards recommend using certain probabilistic-statistical methods as methods of calculation of reliability of structures and bases at the operational stage. However such methods can be applied only when there is total statistical information about monitored parameters of computable models. In practice, at the operational stage, such information is often not complete and consequently probabilistic-statistical methods for foundation bed can not be used. The methods for calculating the reliability of foundation bed of buildings and structures on the operational stage with limited (incomplete) statistical information on the monitored parameters of computable models by the strength criteria and the following notes on the calculation of the reliability of the base by the deformation criteria are given in the article. There are two ways of calculations of reliability regarding to the real conditions of collecting information on the monitored parameters. The first method features description of the functions of random variables distribution capabilities, and in the second method the random variables (parameters) are described by distribution functions obtained from the Chebyshev’s inequality.