Laboratory studies have shown a significant influence of certain fragrances on affective as well as cognitive states in humans. The aim of the current study was to measure the relationship between complex, natural odors and affective states, that is, calmness, alertness, and mood, in the field. In 4 experiments, the emotional impact, intensity, and hedonics of complex, natural plant odors were assessed in 32 healthy human subjects and compared with control conditions involving a similar outdoor environment without the tested fragrant plants. In all experiments, the selected fragrances were evaluated as more intense than the odors in the control conditions but pleasantness ratings differed only in 2 of the 4 experiments. The fragrances improved subjective ratings of calmness, alertness, and mood depending on the sequence of the conditions but independent of visual features of the environment. In contrast, a fifth experiment which tested the influence of natural and artificial pleasant odors and an artificial unpleasant odor on calmness, alertness, and mood in 22 subjects showed that the unpleasant odor impaired these affective states in humans independent of the order of presentation. On the other hand, no effects of the pleasant odors on mood and calmness were observed in this experiment.