An assessment of fuel utilization in Kozloduy NPP units 1-6 is made on the basis of operational data obtained for a total of 62 fuel cycles. Basic characteristics of core loading and operation conditions are given. SPPS-1 and BIPR-7 codes are used to calculate assembly-wise power distributions for different full power days of a given cycle and unit. The data are compared with the measured values of these quantities. The analysis performed shows that the core loading option chosen has led to efficient fuel utilization without violation of the nuclear safety criteria. For WWER-440 (Units 1 - 4) this is expressed in effective reduction of the reactor vessel irradiation, maintaining the design duration of the fuel cycles at a reduced number of assemblies by a factor 5 - 5-10%, utilizing fuel with higher enrichment and implementing the 4-year fuel cycle. For WWER-1000 the improvements lead to: adoption of the 3-year fuel cycle utilizing fuel with 4.4% initial enrichment, implementation of improved fuel with a new type of absorbers and more effective low-leakage core loading patterns. 10 tabs., 6 figs., 7 refs.