The present invention provides methods and devices for reducing the coating variability of a transdermal microprojection delivery device. The device has one or more stratum corneum-piercing microprojections, wherein each microprojection has a maximum width located in the range of approximately 25% to 75% of the length of the microprojection and wherein the microprojection has a minimum width proximal to the maximum width. Preferably, the microprojection has a coating of a biologically active agent that at a minimum extends to at least approximately 75% of the distance from the distal tip to a location corresponding to the maximum width and at most extends up to approximately 90% of the length of the microprojection.
