This paper defines the variations in the reporting of skin smears between a base and field laboratory in a leprosy control program. Ten percent of all slides read by the field laboratory in a control area were re-read by the base laboratory. There was almost no variation in the reporting of negative slides, but a variation of 1 + was present in approximately 92% of positive slides. Thus, there was agreement in approximately 8% of positive slides. This paper also defines the variations in the reporting of positive slides under "ideal" conditions by describing the results of a study on intra- and inter-observer variations among technicians at the base laboratory. There was between 45% and 55% agreement within observers and about 36% agreement between observers. The results of both studies are compared. Simple guidelines are derived to monitor the reporting of skin smears in leprosy control programs.