Abstract: Disclosed is a method and an arrangement for determining the shape and/or size of a freely falling drop (1) of molten glass. One end of the drop is detected by means of two photo-diodes (7,8) spaced apart along the fall path for determining the fall speed of the drop. An image of that part of the drop located momentarily between the two photo-diodes (7,8) is projected onto an elongated photo-diode array (9) extending perpendicularly to the fall direction. The photo-diode array (9) is scanned periodically at a given time interval a large number of times during movement of the drop past the array. This provides information relating to the width of the drop at a large number of locations along the length of the drop. The mutual distance between these width determinations are calculated on the basis of the fall speed of the drop and the time interval between the different scans. The shape and size of the drop is calculated from these data.