In this review, both the newer noninvasive (ie, those that pose no breach of an epithelial barrier) and minimally invasive techniques relevant to the treatment of the critically ill or injured patient will be discussed. In some cases, the development of the technology is so recent that published data describing their clinical applications may be scant. The emphasis herein is on newer technologies; therefore, the discussion of certain established noninvasive techniques, such as pulse oximetry, and minimally invasive therapies, such as percutaneous abscess drainage, will be deferred.