The participating institutes of the National Institutes of Health invite the small business community to apply cutting edge-technology to develop new approaches and chemical modifications that will increase the long term stability, delivery and targeting of siRNAs in cells and tissues for laboratory and therapeutic applications. The number of awards made under this solicitation will depend on the overall scientific merit of the applications and the availability of funds. This PA uses the SBIR and STTR mechanisms. Only small business concerns are eligible to submit applications. Eligible principal investigators include any individual with the skills, knowledge, and resources necessary to carry out the proposed research. On an SBIR application, the principal investigator must have his/her primary employment (more than 50%) with the small business at the time of award and for the duration of the project. The PI on an STTR application may be employed with the small business concern or the participating non-profit research institution as long as s/he has a formal appointment with or commitment to the applicant small business concern, which is characterized by an official relationship between the small business concern and that individual. The NIH will accept as many "different" applications as the applicant organization chooses.