Circular　RNAs　(circRNAs)　are　pervasively　expressed　circles　of　non-coding　RNAs.　Even　though　many　circRNAs　have　been　reported　in　humans,　their　expression　patterns　and　functions　remain　poorly　understood.　In　this　study,　we　employed　a　pipeline　named　RAISE　to　detect　circRNAs　in　RNA-seq　data.　RAISE　can　fully　characterize　circRNA　structure　and　abundance.　We　evaluated　inter-individual　variations　in　circRNA　expression　in　humans　by　applying　this　pipeline　to　numerous　non-poly(A)-selected　RNA-seq　data.　We　identified　59,128　circRNA　candidates　in　61　human　liver　samples,　with　almost　no　overlap　in　the　circRNA　of　the　recruited　samples.　Approximately　89%　of　the　circRNAs　were　detected　in　one　or　two　samples.　In　comparison,　10%　of　the　linear　mRNAs　and　non-coding　RNAs　were　detected　in　each　sample.　We　estimated　the　variation　in　other　tissues,　especially　the　circRNA　high-abundance　tissues,　in　advance.　Only　0.5%　of　the　50,631　brain　circRNA　candidates　were　shared　among　the　30　recruited　brain　samples,　which　is　similar　to　the　proportion　in　liver.　Moreover,　we　found　inter-and　intra-individual　diversity　in　circRNAs　expression　in　the　granulocyte　RNA-seq　data　from　seven　individuals　sampled　3　times　at　one-month　intervals.　Our　findings　suggest　that　careful　consideration　of　inter-individual　diversity　is　required　when　extensively　identifying　human　circRNAs　or　proposing　their　use　as　potential　biomarkers　and　therapeutic　targets　in　disease.