Fluid ejection systems fabricated using MEMS (microelectromechanical systems) technology have a wide variety of applications ranging from ink jet thermal printing  to drug delivery for medical applications . Microfluidic MEMS drop ejectors accurately control the volume and velocity of fluid dispensed. For the electrostatic drop ejector to function properly, the fluid must be contamination free, inert to the MEMS components and inert to materials and epoxies used for packaging. This paper will discuss the failure mechanisms and analysis techniques used to diagnose root cause(s) of failure in as-fabricated (unreleased) drop ejectors, and released, packaged drop ejectors tested in both air and water. Corrective actions implemented to mitigate the failure mechanisms and improve performance and reliability at both the wafer/die level and packaged level will be discussed.