Several thermal treatments simulating forest-fire effects were applied to the seeds of six Cistus species to ascertain both the maximum temperature endured, and the temperature interval needed to break their dormancy. The greatest lengthening capacity of the hypocotyls was also determined. Taking into account the typical temperatures reached in the soil profile during several forest-fire regimes, together with both the lengthening capacity of the hypocotyls, and the germinative behaviour after different thermal pulses of the seeds, we established a theoretical range of burying depth at which these seeds endure the pyrogenic heat pulse, break their dormancy, germinate, and emerge from the soil. For buried seeds, the data revealed three groups with different tolerance to forest fires: the cluster of C. crispus, C. ladanifer and C. monspeliensis, and the cluster of C. albidus and C. populifolius, which withstood thermal pulses of low and high intensity, respectively; and C. salvifolius, which withstood moderate-intensity heat pulses. The data analysis indicated that elongation capacity of the hypocotyls accounted for the above interspecific differences. In addition, some traits of the seeds as size, and capacity of dissemination away the mother-plant, together with soil texture and fire regime are discussed to in terms of the interspecific differences in post-fire colonization behaviour of these species.