The National Testing Institute's new balance, Masscomparator 1, are intended for comparing masses with the utmost accuracy. The equipment of this balance includes a rotary table with space for four weights. If the masses of these four weights are A, B, C and N kg, where N denotes the mass of the standard, the unknown masses A, B and C can be compared according to three principles: 1. Simple comparison: A-N, B-N, C-N. 2. Comparison in "triangle": A-B-N, B-C-N. 3. Comparison in "rectangle": A-B-C-N. In triangular and rectangular comparison respectively, error compensation procedures can be employed which can give more accurate measurements than those obtainable by simple comparison. When triangular comparison is concerned, two essentially different procedures are being developed for the correction of measurement errors. One procedure is based on the least squares method and the second calculates corrections proportional to standard deviations. For rectangular comparison, six equations are derived for optimum correction of measurement errors by the least squares method.