Summary: Estimation of the ratio of two totals is considered, when a probability sample from the finite population is available. Four estimators of the ratio are examined. The first one -- called ``simple'' -- is the ratio of the Horvitz-Thompson estimators of totals; the second -- the ratio of two ratio estimators of totals; the third one -- the ratio of two regression estimators of totals. The fourth one is a calibrated estimator of the ratio. The variances of these estimators are compared. The properties of such estimators of the ratio are studied. Simulation results are presented.