KLA-Tencor has developed a new reticle defect inspection algorithm, APA (advanced performance algorithm), which replaces the current 300 series algorithm (P183), and offers significant improvements in the detection of important defect types on advanced reticles, including OPC reticles. The improvements with APA can also allow inspections with larger pixel sizes compared with P183, resulting in faster inspection times. A suite of test masks was used for evaluating APA's performance on a 351 reticle inspection system at 488 nm using 0.5, 0.375 and 0.25 micrometer pixel sizes. The test suite included a VeriThoroTM 890EX test reticle and a SEMI- standard programmed defect test pattern scaled by 50%, 33%, 25%, and 20% (producing nominal primary features sizes of 1.5, 1.0, 0.75 and 0.60 micrometer). APA's improved performance allowed the use of the 0.375 micrometer pixel size for the 1.5 and 1.0 micrometer linewidth patterns resulting in faster inspection times (compared with the 0.25 micrometer pixel size for P183); it further allowed the successful inspection of the 0.75 and 0.60 micrometer linewidth patterns. A methodology was developed to analyze, summarize and compare the performance results of APA and P183. Finally, APA successfully inspected various actual product reticles with patterns of 0.75 micrometer and below including an advanced MicroUnity OPC (optical proximity correction) reticle with 0.75 micrometer serif and 0.35 micrometer database neck dimensions.