Abstract: Catheters with deployable instruments (e.g., needles) can damage tissue if the instrument unintentionally deploys during use. Described herein are devices and methods for controlling the position of a deployable catheter instrument. In one embodiment, a catheter can include an instrument slidably disposed within an inner lumen of the catheter and coupled to at least one protrusion, as well as a retraction stop coupled to the catheter. The catheter can further include a biasing element coupled to the instrument that can urge the instrument proximally such that the at least one protrusion abuts against the retraction stop, as well as an advancing mechanism to selectively engage the instrument and urge it distally. In some embodiments, the biasing element can be omitted and a deployment stop can be included distal to the retraction stop. These configurations can prevent unintentional instrument deployment and provide greater positioning precision during instrument deployment.