One factor this can easily boil down to is the amount of resources that a company has. Should the company have the time, manpower, and money to invest in a trial, they should certainly undergo the trial themselves rather than sending it out to a CRO. There tends to be a higher amount of traceability and control when things are done in house rather than outside. That being said, I agree with what one person said about resource availability. If doing the clinical trial in house means losing resources that could be doing other things, then using a CRO may be wiser. Generally, smaller companies that don’t have the equipment/trained personnel/money to do clinical trials themselves should rely on CRO’s. Of course, it will not be this cut and dry. I believe even larger companies actually do a mix of sending some of their clincial trials to CRO’s and doing some of them inhouse, just by nature of what their competencies are in. CRO’s can have a wide range of capabilities that a company may not have (access to certain animals, clearances and approvals, personnel trained in a wide range of procedures, experience, etc) that can fill the gap that a company has.