Multilevel Fixed and Sequential Acceptance Sampling: The R Package MFSAS. Multilevel acceptance sampling for attributes is used to decide whether a lot from an incoming shipment or outgoing production is accepted or rejected when the product has multiple levels of product quality or multiple types of (mutually exclusive) possible defects. This paper describes a package which provides the tools to create, evaluate, plot, and display the acceptance sampling plans for such lots for both fixed and sequential sampling. The functions for calculating cumulative probabilities for several common multivariate distributions (which are needed in the package) are provided as well.