The aim of the present report is to review the main scientific literature about polychlorinated dibenzofurans (PCDFs) and to focus the critical aspects of their identification and assessment of exposure. The 2,3,4,7,8- Pentachlorodibenzofuran (PeCDF) has been classified as carcinogenic to humans and included in Group 1 by IARC, as there is sufficient evidence of carcinogenicity in experimental animals and specific action mechanisms. Experimental studies demonstrated that PeCDF interacts through the binding with the aryl hydrocarbon receptor (AhR) as the 2,3,7,8-tetrachlorodibenzo-para dioxin (TCDD). The epidemiological studies on human exposure are limited to few cohort evaluations like the "Yusho" and "Yucheng" incidents, Swedish fishermen cohorts and workers employed in herbicide production. The PCDF as a group may be therefore classified at limited evidence of carcinogenicity. This paper concludes the cycle of review about other POPs, i.e. dioxins and PCBs.