Abstract: An infusion system capable of intravenous administration of fluid to a patient has a drop chamber, including a plurality of drop tubes having drop forming orifices of different preselected cross-sectional areas for forming droplets of different sizes and volumes of the same given fluid, selection means for selecting the drop tube through which the administered fluid will pass and a metering chamber to allow the rate of droplet flow to be observed. The drop tube having a drop orifice capable of producing droplets of the desired size and volume appropriate for the viscosity and purpose of the fluid being administered is selected and a conventional fluid flow rate control device is adjusted, while the drop rate is observed, to set the fluid flow rate.