CD30/Ki-1 positive anaplastic large cell lymphoma (Ki-1 ALCL) frequently exhibits extranodal disease and chromosomal t(2;5)(p23;q35). An 11-year-old girl presented with an intramuscular tumor of the right upper arm. Tumors of the chest wall, left arm and leg, hepatomegaly, pleural effusion, and enlarged lymph nodes then developed. The intramuscular tumor and pleural effusion showed a diffuse infiltration of large atypical cells with abundant amphophilic cytoplasms. The tumor cells were positive for CD30, CD2, CD45RO, and p80, but were negative for other T-cell, B-cell, and myeloid cell antigens. She was diagnosed as having Ki-1 ALCL with a T-cell origin. Cytogenetic studies showed an abnormal karyotype including a der(17)t(1;17)(q11;p11). She received seven cycles of intensive chemotherapy followed by an autologous peripheral blood stem cell transplantation, and has been in complete remission for more than two years. The primary involvement of skeletal muscle is quite uncommon in ALCL, and an abnormal karyotype including t(1;17)(q11;p11) has not been reported previously. Since a high frequency of aberrations of 1p36/1q12 or 17p13.3 was detected in sarcoma cells, the presence of suppressor genes is suggestive in these sites.