The aim of this study is to verify whether the hypertrophy of contralateral testis may predict the absence of the non-palpable testis in the boys younger than 24months of age. According to the previous studies of other countries, the large size of the contralateral testis of the nonpalpable testis has positive correlation woth the weak viability of the affected testis. We are going to evaluate this hypothesis with prospective study. 3 groups are going to be enrolled into this study ; non-palpable testis group(Group1), palpable but not normally descended testis group(group2) and control group(group3). The size of testis will be measured with Ultrasound and the length, width and the height will be measured before surgery at outpatient department. For the group 1 & 2, the viability of the affected testis will be evaluated and compared after surgery. In addition the comparison with normal control group is also going th be conducted.

Inclusion Criteria:

1. neonates or Infants who visited the out-patient clinic with nonpalpable or undescended testis.(group 1, 2) aged from 6months to 18months
2. neonates or Infants aged from 6months to 18months with normal testis (volunteers, Group3)

Exclusion Criteria:

1. previous history of hormonal therapy.
2. chromosomal abnormality
3. previous history of abdomen or inguinal area surgery
4. children diagnosed with epididymitis or orchitis
5. twin baby
6. infants with premature (<37 weeks) birth history

totally, 72 children : unpalpable testis : 24 children, palpable undescended testis : 24 children, normal control : 24 children