Objectives: To evaluate preanalytic factors contributing to failure of next-generation sequencing (NGS) assays. Methods: AmpliSeq Cancer Hotspot Panel was conducted in 1, 121 of 1, 152 formalin-fixed paraffin-embedded tissues submitted to a clinical laboratory, including 493 small biopsy or fine needle aspiration (FNA) specimens (44%) and 25 metastatic bone specimens (2.2%). Results: Single nucleotide mutations and/or insertion/deletion mutations were detected in 702 specimens. Thirtyeight specimens (3.4%) were reported as "no results" due to NGS assay failure. Higher failure rates were observed in specimens submitted for lung cancer panel and melanoma panel (3.1% and 3.7% vs 1.0% colorectal cancer panel), metastatic bone specimens (36% vs 2.6% nonbone specimens), referred specimens (5.0% vs 1.8% in-house specimens), and small biopsy and FNA specimens (5.8% and 3.1% vs 0.7% resection/excision specimens). Test feasibility was higher in in-house specimens than referred specimens (99.1% vs 96.9% in resection specimens, 94.4% vs 87.3% in small biopsy specimens, and 94.3% vs 58.8% in FNA specimens). Conclusions: NGS assays demonstrated clinical utility in solid tumor specimens, including those taken by biopsy or FNA. Preanalytic factors identified by this study that may contribute to NGS assay failure highlight the need for pathologists to revisit tissue processing protocols in order to better optimize cancer mutational profiling.