RE CENT studies have familiarized students of the urban community with the fact that the ideal-type concentric zonal pattern by which the North American city has been described was literally reversed in the Spanish American colonial city.1 Cities were laid out in Spanish America according to a set of planning principles written into the Laws of the Indies. Major public and commercial buildings were grouped around a central plaza. Surrounding this core were the residences of the upper class. homes of the less prosperous Spaniards, Creoles, and Mestizos formed a third and final zone within the city proper. Just beyond the platted area grew up semi-autonomous villages of Indians who, together with the few Negro slaves, constituted the laboring class. In general, housing and social status declined along a gradient drawn in any direction from the plaza to the edge of the city. Some smaller cities have kept this pattern virtually unchanged, except that with the blurring of racial distinctions, the peripheral Indian villages have been generally incorporated into the larger community as zones of lower-class housing. studies to date show a correlation between the degree of deviation from the colonial pattern and the size and rate of growth of the city. Cosmopolitan and booming City shows the greatest change. Provincial and comparatively stable towns such as Oaxaca in southern retain much of the colonial plan. What ecological structure will Spanish American cities assume with further growth and industrialization? Will they inevitably come to resemble more and more the cities north of the Rio Grande? Or will they develop a new but distinct form of their own? A definitive answer to this question-a significant one for comparative urban sociology-is not yet possible from the available evidence. Hayner, writing in 1945, suggested tentatively that City is moving toward the North American zonal arrangement,2 and Leonard, from his study of Paz, came to the same conclusion.3 On the other hand, the capital of Guatemala seems to have grown into a moderately large city without really radical departure from the traditional plan.4 research reported in this paper5 may throw some additional light upon urban ecological trends in the Spanish American area, although the authors realize that their conclusions should not be generalized beyond Guadalajara without further investigation. Except for Guadalajara is larger than any city yet reported in the literature. It is growing rapidly and the breakdown of the classical pattern is far advanced. Yet here an essentially new ecological form, shaped by the adaptation of stable elements in the Mexican urban complex to the necessities demanded by growth and modern technology, seems to be emerging-a form which is different from either the colonial pattern or that typical of North American cities. 1 Asael T. Hansen, The Ecology of a Latin American City, in E. B. Reuter (ed.), Race and Culture Contacts (New York: McGraw-Hill Book Co., 1934), pp. 124-142; Norman S. Hayner, Oaxaca, City of Old Mexico, Sociology and Social Research, 29 (NovemberDecember 1944), pp. 87-95; N. S. Hayner, Mexico Its Growth and Configuration, American Journal of Sociology, 50 (January 1945), pp. 295-304; N. S. Hayner, Criminogenic Zones in City, American Sociological Review, 11 (August 1946), pp. 428-438; Dan Stanislawski, Early Spanish Town Planning in the New World, Geographical Review, 37 (January 1947), pp. 95-105; Olen E. Leonard, La Paz, Bolivia: Its Population and Growth, American Sociological Review, 13 (August 1948), pp. 448-454; Harry B. and Audrey E. Hawthorn, The Shape of a City: Some Observations on Sucre, Bolivia, Sociology and Social Research, 33 (November-December 1948), pp. 87-91; Theodore Caplow, The Social Ecology of Guatemala City, Social Forces, 28 (December 1949), pp. 113-133. 2N. S. Hayner, Mexico Its Growth and Configuration, loc. cit., p. 304. 3 Olen E. Leonard, La Paz, Bolivia: Its Population and Growth, loc. cit., p. 454. 4 Theodore Caplow, The Social Ecology of Guatemala City, loc. cit., passim. 5 field work was done between June 15 and September 1, 1951.