The possible advantages of breast-conserving surgery over mastectomy with respect to psychosocial adjustment were assessed in an interview study. Consecutive patients 40 to 80 years of age with invasive breast cancer of Stages I and I1 were eligible for the study. Of 161 women, 99 agreed to participate; 37 received breast-conserving treatment and 62 received a modified radical mastectomy. The study method consisted of a semistructured interview a t 4 and 13 months after primary treatment based on the Social Adjustment Scale (SAS) and two scales for the estimation of anxiety, depression, and adjustment to a sexual relationship. The women's ratings in the SAS inventory for adjustment to work, social life, marriage, sexual relationship, and parental role showed no statistically significant differences between the two groups. In the interviewer's global rating in the SAS protocol of the overall adjustment after 13 months, 22.0% of the women in the mastectomy group versus 5.4% of those with a preserved breast were rated as having significant disturbances. A statistically nonsignificant tendency (P > 0.05) emerged for the other ratings in the interviewer's assessment in SAS and in the estimation of anxiety, depression, and adjustment to sexual relationships. The consistent tendency indicates that there might be clinically important differences in the psychosocial adjustment after the two treatment methods. Larger trials focused more sensitively on the problems after breast loss versus breast preservation in breast cancer surgery are needed to further explore this field.