Ghrelin affects viability of canine mammary carcinoma cells. The canine mammary cancer cells viability determined by MTT assay in control conditions (ctrl) and in a presence of n-octanoylated ghrelin peptide (Peptides International) at concentrations of 1, 10, 100 and 1000 nM for 24 h. Absorbance at 570 nm has been converted to percentages above control (±SEM). The experiment has been conducted in n = 15 repetitions. Ghrelin treatment at the concentration of 1 and 10 nM; 1 and 100 nM, 1-1000 nM significantly increased cell viability of the CMT-W1 (A), CMT-W1M (B) and CMT-W2 (C) cell lines, respectively. No significant differences has been observed in CMT-W2M cell line (D). The statistical analysis was performed using Prism version 5.00 software (GraphPad Software, USA). One-way ANOVA followed by Dunnett’s post hoc comparisons were applied. p < 0.05 was marked as *, p < 0.01 was marked as ** and p < 0.001 was marked as ***.