Abstract: Since the founding of the People's Republic of China, considerable progress has been made in the scientific investigations of the tropical realm of this co-vntry.In this undertaking, Dr.Zhu Kezhen (Co-Ching Chu) is remembered as a pioneer and organizer.His qualities of clarity of mind an calmness of judgement together with the breadth of his knowledge and interests stretching across the boundaries of numerous branches of scieace made him a shining leader directing multidisciplinary studies to the right quarter. His opinions were generally based on a sure grasp of the complexities of the tropical environment. Most of his vi ews still hold good today, inspite of the rapid advances in the knowledge of the tropical world in China and abroad.Two topics,the demarcation of the tropical and sub-tropical belts in China and the prospects of the development of Hainan, will be discussed in the present paper. Tht former is the subject of part (I).In the latter half of the fifties, a working commission of physico-geographic regionalization of China was established under the Chinese Academy of Sciences, Dr.Zhu was then, vice-president of the academy and chairman of the commission. Shortly after the start of the work, the delimitation of the tropical and subtropical belts of China and coordination and unification of different kinds of physico-geographic regionalization with respect to terms and boundaries to be adopted for identifying the temperature conditions were among the difficulties confronting us.His suggestion to provide an answer to the first problem was that the polar limit of the subtropical belt should lie on the Qinling-Huaihe line, whereas the boundary between the tropical and subtropical belts should cut across the Leizhou peninsula and Taiwan Province.This was quite apart from the schemes advocated at that time by most Soviet scientists, who insisted on shifting both boundaries to much higher latitudes.His proposed solution for the second problem was the proposition that a thermal belt should above all be a climatolo-gical term. The identification of a thermal belt should primarily be the responsibility of climatologists. Since our regional schemes would appear in a range of publications and other documents, and there would be a wide spectrum of readers; it would not be a good idea, if the same designation of temperature regimes would mean quite differently in a series of writings from the same working commission of the Chineee Academy of Sciences. Although discussions and consultations with scientists of other disciplines should be undertaken before the climatologists formulated their systems and criteria, it might happen that there would exist difficulties for regionalization of some other kinds to follow the climatological formulation with regard to thermal conditions. In such cases, thermal belts might be excluded from their nomenclature.This would be desirable where thermal regimes played an unimportant role. There might be a further possibility as exemplified by the soil regions.lt would be helpful, if not also for other reasons, to include warm temperate, subtropical, tropical and other similar predicates in their classification to signify the temperature conditions, under which a set of soils occur, and to which soil utilization and management should be adapted.Both proposals of Dr.Zhu were accepted by the commission. Ensuing to the circulation of draft reports of the commission, pros and cons were scattered in publications, symposia and conversations. One focus of debate was where should be the norhern boundary of the tropical belt. On one extreme, a number of scientists would like to confine the tropical realm to Hainan and other islands of the South China Sea. In their opinion, even Hainan and southern Taiwan were not typically tropical. On the other extreme was the tendency to shift the boundary to encompass middle Guangdong and Guangxi and northern Taiwan, or to the water divide of Nanling and beyond.