Monterey pine street trees within Carmel, California and its immediate vicinity, as well as forest-grown Monterey pine within adjacent natural stands, were sampled with regard to visual stress characteristics, and various environmental and biological variables. Two stress indices were computed, one hypothesized before data collection was based on relative foliage retention and color; the other was derived through principal component analysis of 10 visual stress characteristics. Both indices were highly correlated (r = 0·89). The more closed and generally denser forest stands led to increased plant competition that induced higher levels of stress for forest trees less than 50 cm in diameter when compared with urban street trees of comparable diameters. Urban tree stress generally increased with tree size due to increased internal shading of branches and loss of shade tolerance associated with aging. Differences in stress levels and stress factors are discussed from the standpoint of landscape ecology and implications for tree management are presented.