Aqueous solutions of poly-N-vinylpirrolidone (PVP), a typical polymer for medical purposes, containing sulphuretted tetraphenylporphirine dihydrochloride (H2TPPS4(HCl)2 or TPPS) having antiviral and therapeutic properties were studied. The association of PVP chains due to their nonvalent interactions with TPPS molecules playing the role of interchain and intrachain bonds was observed in complex solution over the temperature range from 20 to 90°C. The character of conformation changes of the polymer was determined; parameters of PVP binding with TPPS were calculated. The TPPS molecules were shown to be associated with PVP ones by means of hydrogen bonds between porphyrin sulfonic groups and polarized water molecules in the polymer hydration shell.