In this catalog a complete list of new publications which include CO observations of external galaxies has been edited so that new observations are reported only once, preferably in refereed journals (pub.dat). Therefore the catalog of publications also serves as an inventory of distinct observational projects. This catalog lists all publications that have appeared since the submission of Verter (1985) and before the end of 1989. For each publication, the number and nature of the observations are summarized. Introduction: This paper is a five year update to the Verter (1985) catalog of CO observations of galaxies. The goal of the present catalog is to give an overview of recent research on extragalactic molecular gas, as conducted through observations of emission from CO isotopes. This overview is intended to cover the number of galaxies observed, the nature of the observations, the number of individuals involved, the telescopes used, the degree of international, multi-observatory, and multi-wavelength collaboration, etc. The heart of the catalog is a complete inventory (Table 1) of research projects incorporating CO observations of galaxies which were published in 1985 - 1989, and a summary of their contents (Table 2). The Verter (1985) catalog contained all observations of CO isotopes in galaxies that were published, or available to the author in preprint form, prior to summer 1984. It contained data from 84 papers. The data were listed by individual galaxy; there were 94 galaxy detections and approximately 200 upper limits known at that time. The present catalog lists all published reports containing new observations of CO isotopes in galaxies that have appeared since the Verter (1985) catalog, through the end of 1989. This includes work which was incorporated in Verter (1985) in preprint form and was subsequently published. No preprints are included in the present catalog because it is too difficult to compile a complete listing of submitted work. This catalog contains 142 publications. The number of galaxies with CO detections is now approximately = 650, too large to list individually. Publication List: pub.dat is an alphabetical listing of the 142 publications containing observations of CO isotopes in galaxies. For each article, the reference and the title are provided. A comment in parentheses indicates those articles which were incorporated in Verter (1985) in preprint form. pub.dat was compiled with three goals: (1) to be as complete as possible in recording CO observations of galaxies, (2) to avoid repetition, and (3) to emphasize refereed publications. The completeness of the catalog is fairly easy to insure. Initially, pub.dat was developed over the past five years by perusing the literature on a regular basis and maintaining a list of articles that referred to molecular observations of galaxies. Finally, the completeness of the list was checked by going through the yearly indices of the refereed journals Ap. J., Astron. and Ap., A. J., M.N.R.A.S., and Pub. Astron. Soc. Japan}, as well as the subject index of Astronomy and Astrophysics Abstracts}. Preventing repetition of data in the catalog is a more difficult matter. The only insurance that the same data is not covered more than once is to read all of the articles and become familiar with their contents. In this manner it becomes obvious if the same observations were reported under different permutations of the authors' names or in different contexts. pub.dat only lists publications which present new observations, and does not include analyses of previously reported data. For example, pub.dat lists Verter (1987), which derives a luminosity function from reported observations, but does not list Verter (1988), which uses the same observations in a correlation study. Because of the preference for refereed journal articles, the following types of research reports appear in pub.dat only if they have not been superseeded by a refereed journal article on the same project: Ph.D. theses, conference proceedings, B.A.A.S. abstracts, articles in the ESO Messenger, etc. When non-refereed sources are cited, only one, preferably most recent, report will be listed for a given project. There is one set of exceptions to the above rules, made on behalf of the Five College Radio Astronomy Observatory (FCRAO) Extragalactic CO Survey. This survey is a multi-year effort to observe CO(1-0) emission in a large and complete sample of galaxies. The selection criteria are: all galaxies at declination above -20deg. with B(T) < 12 mag, or 100 microns IR flux density > 10 Jy, or 60 microns IR flux density > 5 Jy. The FCRAO Survey is by far the largest source of new galaxy detections in CO; by the beginning of 1990 about 270 galaxies had been observed, and about 2/3 of them detected (Young, private communication). Strictly speaking, these detections have been reported in one publication, Young etal. (1989). However, pub.dat lists almost all refereed publications which analyze subsets of this data, even though there is substantial overlap between their samples.