The purpose of this study is to evaluate the tolerability of a subcutaneous needle-free injection device used to administer Fuzeon, compared with the standard needle/syringe supplied with commercial Fuzeon. The anticipated time on study treatment is <3 months, and the target sample size is <100 individuals.

Inclusion Criteria:

• male or female patients, >=18 years of age with HIV-1 infection;
• previously treated with antiretroviral agents.

Exclusion Criteria:

• prior use of Fuzeon or T-1249;
• inability to self-inject;
• active, untreated opportunistic infection.