Milt was collected from the tench Tinca tinca (L.) following hormonal stimulation with carp pituitary homogenate (CPH, group I, n = 9), Ovopel (group II, n = 8) and Ovaprim (group III, n = 9). Males non-stimulated fish were used as a control (group IV, n = 6). The parameters determined included the total volume of milt (TVM, ml) and the volume per kg of the males’ body weight (VOM, ml kg⁻¹ b.w.), total number of spermatozoa produced by the males (TSP, ×10⁹) and the number of spermatozoa per kg of their body weight (TNS, ×10⁹ kg⁻¹ b.w.). Moreover, attempts were made to show the effect of the hormone preparations on spermatozoa motility (%), their concentration in milt (×10⁹ ml⁻¹) and the total protein content in seminal plasma (mg ml⁻¹). Osmotic pressure of the seminal plasma (mOsm kg⁻¹) was determined to check if the milt samples were contaminated with urine. Pearson’s linear correlation was also determined between the osmolality, on the one hand, and the spermatozoa motility and concentration of spermatozoa in milt of the groups examined in the study, on the other. The significance of differences between the analysed parameters was checked with Tukey’s test (One-way ANOVA, α = 0.05). Motility and concentration of spermatozoa in the remained relatively low, not exceeding 22% and 5.0 · 10⁹ ml⁻¹ in each of the groups. Using CPH, Ovopel or Ovaprim did not result in any significant increase (P > 0.05) in the amount of milt obtained (TVM, VOM) or the total amount of spermatozoa produced as compared to the control group. Significant differences (P < 0.05) were found only between the TNS values for group I (CPH), and group IV (control). Osmolality of the seminal plasma did not exceed 120 mOsm kg⁻¹ in any of the groups under examination. Its low values as well as low motility and low concentration of spermatozoa in milt indicate that milt was contaminated with urine, which is also corroborated by a significant correlation between osmolality and motility of spermatozoa in group III (R² = 0.828; P < 0.001) and IV (R² = 0.983; P < 0.001) and between osmolality and concentration of spermatozoa in each of the groups (R² = 0.447; P < 0.05, group I; R² = 0.964; P < 0.001, group II; R² = 0.768; P < 0.001, group III and R² = 0.924; P < 0.001; group IV).