An empirical investigation of citations to 150 publications in the field of Information and Library Science (ILS) has enabled mapping of the development of the interdisciplinary scope of the ILS field. The publications were drawn randomly in six years between 1975 and 2000, with 25 articles each from the selected years. Network-based graphical presentation of number of extradisciplinary citations show that the field attracts a significant wide spectrum of disciplines in the domains of science, social science, and the humanities, and that the kinds of disciplines interested in the field vary by year. ANOVA result based on the number of extradisciplines was significant and the linear contract between the year group of 1975,1980,1985 and the year group of 1990,1995, 2000 was highly statistically significant. Interdisciplinary diversity was further examined through measures of Citations Outside Category and Brillouin's Index. Kruskal Wallis test showed significant results, however, when the two measures were considered independently, only the contrast of the year of 1990 to the prior three years was significant.