OBJECTIVES: Patient reported outcomes (PROs) have gained a prominent place in clinical research. Previous estimates suggest that PRO measures are used in 14% of clinical trials. Online registries, such as ClinicalTrials.gov, may be useful for updating the extent of PRO use. The objectives of this study were to: (1) estimate the proportion of clinical trials that include at least one PRO measure, and (2) examine associations between trial characteristics and the use of PRO measures. Particular emphasis was given to evaluation of use in oncology studies. METHODS: A local copy of the ClinicalTrials.gov database was made containing all data from November 2007 to December 2013. Content was searched for use of PRO measures. Multivariate logistic regression was used to investigate possible associations between trial-level characteristics and use of PRO measures.  RESULTS: Of 96,736 registered trials, 25,880 (27%) were identified as using one or more PRO measure. Among oncology trials, 29% (3,947/13,584) were identified as using a PRO measure, compared to 26% (21,933/83,152) of non-oncology trials. Trials using PRO measures were more likely to be sponsored by university/research organizations (29%) or the US government (33%); Phase III (35%); randomized (32%); and evaluating devices (30%), procedures (32%) or behaviors (50%), compared to drugs (24%). They were less likely to be regulated by the FDA (23%).  CONCLUSIONS: Between 2007 and 2013, there was an increase in the number of trials using a PRO measure, particularly in oncology trials. The increased use may be attributed, in part, to the changing landscape of patient-centered care and stakeholder engagement in general. With recent initiatives such as the Patient-Focused Drug Development and the NIH-sponsored Patient-Reported Outcomes Measurement Information System, the use of PRO measures in clinical research will likely increase further.