The flora of San Pietro Avellana municipality (Alto Molise) - A first contribution to the flora of a little township in Alto Molise, characterized by the presence of “old growth forest”, is offered. In the present survey 557 taxa have been recorded; they belong to 292 genus and 75 families. The most represented family is Asteraceae (Compositae) with 53 taxa followed by Fabaceae (51 taxa) and Poaceae (43 taxa). Most frequent genus are Lathyrus, Orchis and Ranunculus with 10 taxa for each one. The life form spectrum highlights the dominance of hemicriptophytes (48%) followed by geophytes (18%), pointing out the mountain connotation of the study area. The chorologic spectrum is dominated by the Eurasian chorotype (34%), because of the vicinity with the European phytocoenosis. A considerable note for the recorded of Himanthoglossum adriaticum H. Baumann, a rare orchid listed in the Habitat Directive Annex II.