The Purpose of this study was to build a substan tive theory about the experience of postpartum depression. The qualitative research method used was grounded theory. The interviewees were eight mothers who had experienced postpartum depression. The data were collected through in-depth interviews with audiotape recording done by the investigator over a period of twelve months. The data were analyzed simultaniously by a constant comparative method in which new data were continuously coded into categories and properties according to Strauss and Corbin's methodology. Analysis the grounded data resulted in 28 concepts being identified. Eight categories emerged from the analysis. The categories were regret, loss of freedom, isolation of oneself, heartache, loss, emotional upset, avoidance, recovery. These substantive categories are consistant with preious research results. Causal conditions included: regret, loss of freedom. Phenomena: heartache, loss, emotional upset. Context: isolation oneself. Intervention condition: avoidance. Action/interaction strategies: desire for recovery. Consequences: recovery. These categories were synthesized into the core concept-The process of filling the empty loss of self The process of the experienced postpartum depression was (1) change after delivery, (2) searching for a reason for depression, (3) effort to recover from postpartum depression, (4) recovery from postpartum depression and return to previous life. The process of recovery from postpartum depression was proceeded by (1) support from others, especially husband, (2) resolution of stressful life events, (3) reconstructing of life goals and resolution strategies, (4) acceptance of depression and seeking psychiatric treatment. Seven hypotheses were derived from the analysis. (1) Mothers who experienced stressful life event and economic problem are more depressive. (2) Mothers who have conflict with parents are more depressive. (3) The more somatic symptoms, the more depression. (4) Social support faciliates recovery from postpartum depression. (5) Mothers who have lower self-esteem are more depressive. (6) Mother's role overload disturbs recovery from postpartum depression. (7) Ideal maternal identity faciliates recovery from postpartum depression. Through this substantive theory, nurses can understand the importance of postpartum depression management.