OBJECTIVE: Skin basal cell carcinoma (BCC) is the most common malignant skin tumor. Recent studies demonstrated that circular RNAs (circRNAs) are implicated in tumorigenesis and may represent potential therapeutic targets. The aim of the present study was to explore the expression profiles of circRNAs and their role in skin BCC. MATERIALS AND METHODS: Three pairs of skin BCC tissues and adjacent tissues were used to perform a circRNA microarray for screening of circRNA expression profiles. Circ_NCKAP1 was selected as a target circRNA by RT-qPCR verification and bioinformatics analysis. The effect of circ_NCKAP1 knockdown on cell proliferation and apoptosis was assessed using CCK8 and Annexin V-FITC/PI assays, and its regulation over the miR-148b-5p/HSP90 axis was assessed by dual-luciferase reporter assay. RESULTS: Circ_NCKAP1 was found to be significantly upregulated in skin BCC tissues (p<0.05). In vitro loss-of-function assays demonstrated that circ_NCKAP1 knockdown markedly inhibited cell proliferation and promoted cell apoptosis (p<0.05). Moreover, Dual-Luciferase reporter assay identified that circ_NCKAP1 could bind to miR-148b-5p directly, and HSP90 was targeted by miR-148b-5p. CONCLUSIONS: Circ_NCKAP1 can promote skin BCC progression by sponging the miR-148b-5p/HSP90 axis, and circ_NCKAP1 may be a potential target for skin BCC therapy.