Three isomers of pyridylbenzylcarbinol were synthetized and their chemical properties and biological activity were studied. Clear dependence between chemical structure and antitumor activity was observed. As expected most active appeared 2-pyridylbenzylcarbinol (alpha-carbinol). It showed significant antitumor activity against subcutaneous tumors of Ehrlich carcinoma. Nemeth-Kellner lymphoma and sarcoma 180. On a chronic treatment schedule tumor inhibition from 60 to 80% was induced. No activity was seen in L1210 and P388 models. In B16 melanoma the significant inhibition of tumor growth was obtained at 200 mg/kg/injection. Tumor inhibitory effect was also observed in Yoshida sarcoma. Depending on a dose and schedule the increase in lifespan from 45 to 147% was achieved. LD50 and MTD were determined and were 750 +/- 87.65 mg/kg and 557.8 mg/kg, respectively. Only slight suppressive effect of alpha-carbinol on immunological system was showed. It concerned mainly immunological reactions with cellular system involved, in which distinct suppressive effects were noted. Specific and nonspecific humoral reactivity was little or not at all affected by alpha-carbinol.