This is a guide to the organizational units of the United Nations (UN) system that work on environmental issues. Section 1 provides short descriptions of sources of information on the environment from 34 organizations of the UN system. A contact address is given for each organization. Section 2 groups sources of information into 11 subject categories. These are: (1) "Comprehensive Sources"; (2) "Agriculture and Land Use"; (3) "Aquatic Environment"; (4) "Atmosphere and Climatology"; (5) "Demography and Population"; (6) "Energy"; (7) "Human Settlements and Human Health"; (8) "Industry and Transportation"; (9) "Natural Resources"; (10) "Pollution"; and (11) "Statistics." Section 3 describes the directories produced by ACCIS and the depository libraries of the UN system. Eight non-UN organizations producing environmental information are included in section 4. Section 5 lists the addresses of INFOTERRA National Focal Points, sources referenced, and online hosts to UN databases. (YP)