Xerocomus is a genus of poroid fungi related to Boletus. Many mycologists did not originally recognize the distinction between the two genera and placed Xerocomus taxa in genus Boletus. However, several molecular phylogenetic studies have demonstrated that Xerocomus is a heterogeneous genus of polyphyletic origin, which has resulted in further division of Xerocomus into Xerocomellus and Hemileccinum. The members of the genus Xerocomellus are more closely related to Boletus than true Xerocomus is, which is relatively distantly related to Boletus and more closely related to Phylloporus. Other former Xerocomus species have since been moved to Aureoboletus, Imleria, Hortiboletus and Rheubarbariboletus.
Ladurner and Simonini published a monograph on Xerocomus in 2003, but this predated the taxonomical revisions based on phylogenetic inferences. In 2008, Hills included 18 species found in Britain, not including some species sometimes treated as Xerocomus, and including Boletus pulverulentus and Boletus impolitus., currently placed in genera Cyanoboletus and Hemileccinum, respectively. More recent phylogenies have confirmed Xerocomus as monophyletic in its new restricted arrangement.
Most members of Xerocomus are edible, though of mediocre gastronomical value and inferior to the sought-after porcini.
| Spore surface | Smooth | Smooth | Longitudinally striated or smooth, never bacillate | Bacillate | |
| Hymenophoral trama | Boletoid type with gelatinous lateral strata | Boletoid type with gelatinous lateral strata | Intermediate between boletoid and phylloporoid when fully developed with distinct but weakly gelatinous lateral strata | Phylloporoid type with nongelatinous lateral strata | |
| Pileipellis | Trichoderm, sometimes collapsing, rarely ixotrichoderm or other | Initially trichoderm but collapses with age | Initially palisadoderm, typically encrusted | Initially a trichoderm, never encrusted | |
| Lateral stipe stratum | Frequently gelatinous, 60-90 μM thick, thicker than that of Xerocomellus | Similar to that of Leccinum species, ornamented with stipe scabrousities up to 400-640 μM thick | Frequently not present, reduced to no more than 30-40 μM thick, not gelatinous | Lateral stipe stratum never gelatinous and 80-200 μM thick |