A description of mobile Ni contents in various subtypes of calcareous black soils from the area of the mountain massif of Rajac, is given in the present paper. A hundred soil samples were analysed in all, originating from four subtypes of calcareous black soil (organogenic, organo-mineral, brownized and loessivized black soils). The extraction of mobile Ni was carried out with 1.0 N HCl and its content was determined by atomic absorption spectrophotometry. The obtained results indicate that mobile Ni content in the investigated soils varies within a wide range, from 5.0 to 251.3 mg/kg that it is very seldom (only in 3% of the investigated samples) within the range from 5 to 7 mg/kg, that in over 90% of the 100 investigated samples it is higher than 10 mg/kg, and in almost 3/5 of the samples it is higher than 20 mg/kg. Calcareous black soils of Rajac massif have much higher mobile Ni content than previously investigated black soils from calcareous massif of Rtanj, which is, by all means, only partly due to their more severe dealkalization and acidification. In addition, here is undoubtedly apparent the influence of the geological substrate, i.e. of serpentine rocks that border the calcareous massif of Rajac.