This slide presentation outlines information on microbiological method performance quantification issues, three method performance quantification examples, and new tools for quantifying method performance. Specific topics covered include: importance of quantitative assessments; assessing performance of microbiological methods; use of quantitative validation study data; Example 1: EPA Methods 1622 and 1623; approach to quantitative assessment; interlaboratory validation study format; spiking precision and method performance; Cryptosporidium data set comparison; comparison of Cryptosporidium MS recoveries; assessment of minimum recovery QC criteria; Example 2: EPA Method 1605; approach to quantitative assessment/study format; spiking precision and method performance; Example 3: EPA Method 1601; approach to quantitative assessment; spike estimation and method performance; new tools for quantifying method performance; new bacteria spiking option; new protozoa spiking options; and, other new USEPA quantitative microbial methods.