ΕΒΙ089, a vitamin D analogue, induces growth inhibition, differentiation and apoptosis in tumor cells in vitro and in vivo. In this preliminary report we present the effects of EB1089 on tumor size and blood calcium levels, on 16 C3H/Sy mice bearing SMCs. Material-Method One experimental (n=7) and one control groups were formed when a palpable tumor was evident. The former group received 0.5 pg/kg EB1089 every other day, the latter received no treatment. Tumor size was measured at 2.5 weeks after treatment initiation, for both groups. Blood was taken before sacrifice for calcium measurements. Results Our results show that EB1089 statistically decreases the tumor size and prolongs survival, causing also calcium elevation. Conclusions The findings suggest that EB1089, might be a promicing antitumor agent, provided that monitoring of doses will be attended.