There are various methods and implementations for level detection. Optical methods display a rapid growth among these with their high sensitivities and low costs. In this paper, we propose a new method that uses reciprocally placed LEDs and phototransistors whose optical axes are shifted according to each other. Shifting distance is determined by the direction of the change in the fluid level. The minimum value of the shifting distance depends on dimensions of the LED and the phototransistor. The advantage of this method is that optical properties of the liquid do not have significant effects on level detection phenomenon. Our method can be used in detecting levels of water and inflammable fluids (gasoline, fuel oil, alcohol, etc.). (C) 2003 Elsevier B.V. All rights reserved.