The purpose of this study was to build a substantive theory about the experience of the family whose child has died of cancer The qualitative re-search method used was grounded theory. The interviewees were 17 mothers who had cared for a child who had died of cancer Traditionally in Korea, mothers are the care givers in the family and are considered sensitive to the family's thoughts, feelings. The data were collected through in-depth interviews by the investigator over a period of nine months. The data were analyzed simultaniously by a constant comparative method in which new data are continuously coded into categories and properties according to Strauss and Corbin's methodology. The 16 concepts which were found as a result of analyzing the grounded data were, -left over time, the empty place, meaninglessness, inner sadness, situational sadness, heartache, physical pain, guilt, resentment, regret, support / stigmatization, finding meaning in the death, changing attitudes about life and living, changing attitudes about health, changing religious practice and changing family relations. Five categories emerged from the analysis. They were emptiness, consisting of left over time, the empty place and meaninglessness ; sadness, consisting of inner sadness and situational sadness ; pain, consisting of heartache and physical pain ; bitterness, consisting of guilt, resentment, regret, sup-port / stigmatization and finding meaning in the death : and transition, consisiting of changing attitudes about life and living, changing attitudes about health, changing religious practice and changing family relations. These categories were synthesized into the core concept, -the process of filling the empty space. The core phenomenon was emptiness. Emptiness varied with the passing of time, was perceived differently according to support / stigmatization and finding meaning in the death, was followed by sad-ness, pain, and bitterness, and finally resulted in changes in attitudes about life and living and about health, and in changes in religious practice and family relations. The process of filling the empty space proceeded by ① accepting realty, ② searching for the reason for the child's death, ③ controlling the bitter feelings, ④ reconstructing the relationships ameng death, illness and health and ⑤ filling the emptiness by resolving causes of child's death, adopting, having another child or with work. Six hypotheses were derived from the analysis. ① The longer the bereavement, the mere the empty space becomes filled. ② The longer the hospitalization, the more sup-port the family needs. ③ The more the sadness, pain and bitterness are expressed, the mere positive changes emerge. ④ Family support faciliates the process of filling the empty space. ⑤ Higher family cohesiveness faciliates the process of filling the empty space. ⑥ The greater the variety of reasons attributed to the child's death, the greater the variety of patterns of change. Four propositions related to emptiness and bitter-ness were developed. ① When the sense of emptiness is great and bitterness is manifested by severe feelings of guilt and resentment, the longer the process of fill-ing the empty space. ② When the sense of emptiness is great and the family is highly motivated to get rid of the bitterness, the shorter the process of filling the empty space. ③ When the sense of emptiness is less and bitter-ness is manifested by severe feelings of guilt and resentment, the process of filling the empty space is delayed. ④ When the sense of emptiness is less and the family is highly motivated to get rid of the bitterness, the process of filling the empty space goes on to completion. Through this substantive theory, nurses under-stand the importance of emptiness and bitterness in helping the family that has lost a child through cancer fill the empty space. Further research to build substantive theories to explain other losses may con-tribute to a formal theory of how family health is restored after human tragedies are experienced.