By characterizing the composition of road network in the Huzhong Forestry Bureau in Great Xing' an Mountains, Northeast China, we investigated the effects of road networks on landscape pattern by quantifying 1989 landscape pattern for each of the 17 forestry farms on maps with and without roads by principal component analysis (PCA). The results showed that road networks, including the main and secondary timber-transport roads, were distributed evenly among the observed 17 forestry farms with a density of 2.3 m x hm(-2) and spread along the river networks throughout each farm. The emergence of roads significantly altered the landscape pattern at the landscape level in each farm, which was characterized by landscape fragmentation involving a decline in patch area and an increase in patch number and distance among patches. Furthermore, no significant correlation was found between fragmentation and road density. The road network had more impact on fragmentation than on aggregation at the landscape level.