The focus of this paper is to present an inductively derived substantive theory, "Negotiating Uncertainty". The theory details the most salient concerns of families who had a close relative who had suffered a severe TBI and how they dealt with the experience during the uncertain trajectory of illness that followed coma. This study was conducted in two acute care neurosurgical units in Level 1 trauma facilities in Toronto, Canada, using the grounded theory research method. There were a total of 36 participants in the study: 11 individuals who were injured and 25 close family members. Supporting data is provided to permit the reader to hear the issues of family members first-hand and to evaluate the recommendations for practice, education, and research.