The paper presents the research results concerning the impact of rotational speed of a sowing shaft (4-34 rot•min-1), width of a sowing opening (1-5 mm) in a pin sowing unit and width of interrows (7-15 cm) and sowing speed (4-12 km•h-1) on the regularity of dosing Flämingsprof oat seeds at the fixed amount of sowing 156 kg•ha-1, which results from the accepted, recommended stock density of 400 seeds•m-2. Tests were carried out on the laboratory stand in two stages. In the first one, measurements related to determination of the performance characteristic of the tested sowing unit was carried out, in the second one, measurements related to determination of the longitudinal irregularity index of seeds sowing was performed. It was proved that from among the investigated factors, regularity of dosing seeds has significant impact (α=0.05) on the width of interrows, rotational speed of the sowing shaft and the width of the sowing opening. From analysis of regression of many variables with stepwise procedure of elimination of non-significant variables, a second degree equation was obtained, which included independent variables - the width of interrows and the width of the sowing opening. The value of irregularity index of seeds sowing at the change of interrows width from 7 to 15 cm decreased by approx. 35% – from value 0.72 to 0.46.