To study the polymorphism by esterase composition, 61 samples of seeds from the core collection of  Brassica rapa L. (VIR) were examined. The method of native electrophoresis in PAAG with the subsequent processing of the gels revealed 8  main zones of esterase enzymes, which were subdivided into 2 conditional loci - "b" and "c". Five zones of higher molecular weight (41.2kD - 31.9kD) were designated as b1-b5.  Four of them turned out to be monomorphic. Among the zones of locus "b", only b2 (Mr 39.4 kD)  possessed polymorphism. The "c" locus was represented by three lower molecular weight zones (22.6  kD -18 kD), which were designated as c1-c3. These zones were characterized by the highest  polymorphism among the samples presented. According   to   their   esterase   complex,   all   samples   were   divided   into   10   groups  (zymotypes).  The  most  common  was  the  zymotype  1,  36%  of  the  total  number  of genotypes.  The second most common was zymotype 2, its representatives accounted for 19.7%. The maximum number  of esterase enzymes (8 zones) was characterized for the zymotype 5. The zymotype 8 had the smallest  number of esterases (5 zones). The frequency of occurrence of each zone among all genotypes varied from 36 to 89%. The most common  among all polymorphic esterase zones was the zone c2 (Mr 20.4 kD), the frequency of its occurrence  was 89% of the total number of genotypes. The  relative  amount  of  different  isoforms  of  esterase  enzymes  in  samples  varies  significantly. Zones of the locus "b", as a rule, quantitatively dominate over the zones of the  locus "c". The average statistical value of the content of all isoenzymes of locus "b" varies from  14% (zone b2) to 20.28% (zone b4), while f  r enzymes of the locus "c" this value varies from 8.86% (zone c1) to 12.39% (zone c2).