CancerPDF (Cancer Peptidome Database of bioFluids) is a comprehensive database of endogenouspeptides detected in the human biofluids. The peptidome patterns reflect the synthesis, processing and degradation of proteins in the tissue environment and therefore can act as a gold mine to probe the peptide-based cancer biomarkers. Although an extensive data on cancer peptidome has been generated in the recent years, lack of a comprehensive resource restrains the facility to query the growing community knowledge. We have developed the cancer peptidome resource named CancerPDF, to collect and compile all the endogenous peptides isolated from human biofluids in various cancer profiling studies. CancerPDF has 14,367 entries with 9,692 unique peptide sequences corresponding to 2,230 unique precursor proteins from 56 high-throughput studies for ~27 cancer conditions. We have provided an interactive interface to query the endogenous peptides along with the primary information such as m/z, precursor protein, the type of cancer and its regulation status in cancer. To add-on, many web-based tools have been incorporated, which comprise of search, browse and similarity identification modules. We consider that the CancerPDF will be an invaluable resource to unwind the potential of peptidome-based cancer biomarkers. The CancerPDF is available at the web address http://crdd.osdd. net/raghava/cancerpdf/.Cancer is considered as the major public health concern worldwide and the second most health hazardous disease, causing deaths in the United States. Globally 14 million new cases and 8.2 million cancer-related deaths have been reported in 2012 1 . In 2017, there is an approximation of 63,990 new cases and 14,400 deaths from cancer in the United States 2 . Although the rate of survival has increased over the years, still it is meager. The lack of diagnosis at an early stage is one of the major hurdles in treating the cancer patients 3 . Cancer detection is often skewed due to the lack of accurate and non-invasive markers. Due to advances in genomics and proteomics, the probability to detect the cancer at an early stage has improved using peptide-based biomarkers 4 . In recent years, the peptide-based biomarkers have emerged as diagnostic tools in several foodborne diseases 5 , arthritis 6 , inflammatory disease 7 as well as cancer 8,9 . Thus it is imperative to understand the mechanism of action and processing of peptides in mammalian biofluids. Following are the few examples of peptide-based biomarkers; i) Insulin and C-peptide are used in case of diabetes 10 , ii) Calcitonin, and collagen fragments in case of osteoporosis 11-13 , iii) Pro-gastrin-releasing peptide for small cell lung carcinoma 14 , iv) β-amyloid 1-42 for Alzheimer's disease 15 and v) angiotensin II for hypertension 16 .In past, large number of peptide repositories and computational resources have been developed to explore full potential of peptides in medical sciences [17][18][19] . Pepbank is the generalized database of biologically relevant peptides containing nea...