During cross-flow membrane emulsification, droplet formation at a micro- engineered membrane with uniform pores was visualized by microscopy. Although the membrane pores were uniform in size, the obtained emulsions were polydisperse, Observations showed this to be due to steric hindrance of droplets forming simultaneously. At some pores close together, the droplet formation frequencies were almost identical (0.86 and 0.88 s(-1)). This was confirmed by the cross-correlation value (around 0.8). Because the droplets hindered each other during growth, the droplet diameter decreased with an increasing number of active pores. In spite of the uniform pore size and shape, the number of active pores only gradually increased upon increasing transmembrane pressure. We suggest this to be due to the dynamics of the flow of the to-be-dispersed phase towards and through the membrane. Under the process conditions used, interactions can only be prevented by using a membrane with a lower porosity.