The  total  content of heavy  metals  in soil  does not indicate bioavailability  of these  elements after introduction  of sewage  sludge  to soil.  Determination of the rate  of heavy  metal  mobilization from  sewage  sludge  after  its  application  to soil  is  very  important   for  agricultural practice since  it  allows  us  to asses  the rate  at  which  these  elements  pass  into  the soil  solution, which  conditions  their  uptake  by plants.  This research  has  been conducted to assess  the effect of farmyard  manure   and  sewage  sludge  fertilization on  the  amounts  of zinc  and cadmium  absorbed  by  maize  and  the  content  of their   mobile  forms  in  soil. The research  consisted  of a  three-year  pot  experiment. Farmyard  manure   and  sewage  sludge fertilization resulted  in larger total yields of maize biomass (for the 3-year period of the investigations)  than harvested   from  the  treatments  where  only  mineral   compounds  were used  as  fertilizers. Irrespectively of the fertilizer dose,  the  total  (for  3  years)   amounts  of zinc  and  cadmium absorbed by  maize  were  the  highest  in  the  treatments where  only  mineral  salts  were added and  Zn  and  Cd  quantities taken  up  by  maize  in  the  first   year  of the  experiment   contributed to this  result. Fertilization with  farmyard manure  and sewage sludge  did not cause  any significant mobilization  of mobile zinc  and  cadmium  forms  in  soil after  the  first   year  of the research.  As  a  result   of organic  matter  mineralization and  progressing  soil  acidification, in the second  and  third   year  of the  research,  the  content  of mobile  forms  of the  elements in soil increased,  although  to a  lesser  degree than  under  the influence   of exclusively  mineral  treatment.