The subject addressed by this paper is the relationship between the use ofpublic and private open space by families of 2 sub-cultural groups living inmulti-family buildings in Israel. 70 % of the urban population of Israellive in multi-family buildings, and 50 % of the dwelling units are spon-sored in some way by the Ministry of Housing. Until recently the buildingplot was owned and used jointly by all the building residents. However, dueto the need to reduce building costs and to improve the level of maintenanceof the open space area of the buildings the Ministry of Housing has, duringthe last 10 years, experimented with a new policy. Ownership and use of most of the open space of the building plot is allocated solely to the residentsof the first floor apartments.The purpose of the research project was 1) to evaluate the needs of the res-idents of this new building form for three types of open space - neighbor-hood public parks, jointly owned open space of the building (semi-privatespace), and private yards. 2) to identify the special needs of 2 sub-cultural groups distinguished by level of observance of Jewish religiouslaw. These 2 groups differ significantly in family size and life style andthus it is important to determine whether or not this has implications foropen space use. 3) to develop design guidelines for these open space areas.Three newly developed neighborhoods of Jerusalem were studied and 2 otherbuilding forms were used as control groups. The empirical study was car-ried out in 1988-90. 3 research methods were used to examine the behav-ior and attitudes of the residents: a) Individual structured interviews -500residentes were interviewed in their homes. b) Behavior mapping obser-vations in the public and semi-private open spaces. c) On site survey ofthe physical characteristics of the 3 types of open space.Findings with the less observant group only indicate that the existence ofprivate yards provides benefits for the majority of residents. Owner of theyards are able to extend their living environment out of doors, and given thelimited size of their apartment ( an average of 80 m2 ) and the Mediterra-nean climate, this is an important asset. The residents of the upper floorsreport a benefit from the improvement in the appearance of the environ-ment occasioned by the care given the yards, and no negative effect on thefunctioning of the building. However, the existence of the private yards doesnot effect the use of the public and semi-private spaces. Each of the 3 typesserves somewhat different needs and different populations. The private yardis used mainly by the adults or the whole family for activities like rest andentertaining that are extensions of activities linked to the home. The semi-private spaces are used mainly for play and mainly by children aged 6-11.The parks are used mainly for play by younger children accompanied byadults. Thus, our data indicate that each of the 3 types of open space haveseparate functions. One cannot fully substitute for the other. The detaileddesign of the private yards and the semi-private spaces is critical for theirability to fulfill these functions. For the private yards the issue of privacyIs critical and for the semi-private spaces the issues of location, size, to-pography and shade are important. The results of the second part of thestudy will allow us to see whether or not these preliminary conclusions arespecific to this group or more general. The presentation will also includespecific design guidelines for each of the open space types.