The  Woolly  Foxglove  (Digitalis  lanata)   is  one of the  herbal   plants   cultivated  in  Poland.  It is grown as important plant material for production of cardenolides used in the pharmaceutical industry.  The  aim  of the  research  has  been to determine  the  chemical  composition  and mole ratios  in  leaves  of cv.  Victoria Woolly  Foxglove  affected  by mineral   fertilisation.  For this purpose,  a  strict,  one-factor,  micro-plot  field  experiment   was  set  up  in randomised  blocks with  four  replications. The  experimental factor  was  NPK mineral   fertilisation  applied  to  soil  in the  following  doses  per  hectare.  A0  -  no  mineral  fertilisation,  A1 - 40 kg N  + 17.48  kg P  + 49.8  kg K, A2  - 80 kg N  + 34.96  kg P  + 99.6  kg K, A3  - 120  kg N  + 52.44  kg  P  + 149.4  kg K. For  chemical  analyses, samples  of 0.50  kg  of leaves  were taken  from each plot.  Dried, melted and  wet  mineralised in sulphuric(VI) acid,  the  samples were  analysed   and  concentrations   of the  following  elements  were  determined:   nitrogen  by Kjeldahl method,  total  phosphorus  by the  colorimetric  method  with  ammonium  molybdate, potassium,  calcium  and  sodium  by flame photometry,  and  magnesium  by atomic  absorption spectrometry  (AAS).  Mole  ratios of the chemical  elements  in  leaves  were  also  calculated. In  general,  the  use  of mineral   fertilisation induced  a  significant increase  in  the  content  of total  nitrogen,  total  phosphorus  and potassium,   but  reduced  the  sodium  concentration   in leaves  of the  Woolly  Foxglove compared to the  control.  After  the  applied  fertilisation doses, the  K:Ca and  K:Na ratios  in leaves  were  significantly broadened  and  the  Ca:P   ratio  was narrowed.   Significantly  higher values   of the  K:(Ca+Mg)  ratio  were  observed  in  leaves after  applying  the  medium  (A2) and highest  NPK ha-1 (A3)  doses.  The  Ca:Mg  ratio  in leaves  of the  Woolly  Foxglove  was distinctly  narrowed  versus   the  control  after  using  the lowest  fertilisation dose (A1).   However, after  applying  the  medium  dose of NPK (A2),   the K:Mg  ratio was  broader  than  in  the  control treatment.