This study is being offered to all participants of the ACY-5 study as an optional addition to the male contraceptive study in which they participated. Participation is voluntary.

The purpose of this added procedure (Testicular Aspiration-HOP 3) is to determine the amount of testosterone (male hormone) in the testes of men who are on a male contraceptive regimen.

The goal of our contraception study (ACY-5) is to develop a hormonal regimen where in all individuals enrolled achieve azoospermia (zero sperm). However, early data demonstrated that some individuals have persistent sperm in their semen despite treatment. We hope to be able to determine whether differences in intratesticular hormone levels account for persistent sperm production in men who do not reach counts of zero as compared to those who do in the male contraceptive study. This study will measure testosterone levels in the testes of men who are participating in male contraceptive studies. Testosterone will be measured in a small amount of testicular fluid at the end of the study treatment phase after sperm counts have been reduced to zero or very low levels.

Inclusion Criteria:

• Male between 18-55
• In good health
• With normal sperm counts and willing to use an acceptable form of contraception during the study

Exclusion Criteria:

• Male in poor health
• Significant chronic or acute medical illness
• Skin conditions that might interfere with or be exacerbated by testosterone gel
• No history of alcohol, illicit drug or anabolic steroid abuse
• Abnormal reproductive function
• Participation in a long-term male contraceptive study within three months of screening