OBJECTIVES:  Little is known about the equivalence of Web and IVRS survey responses. Given the potential to affect power in clinical trials, the purpose of this study was to assess the equivalence of PRO survey responses across modes (Web, IVRS, and Paper). METHODS: Post-operative colorectal cancer patients at Memorial Sloan-Kettering Cancer Center (MSKCC) with home web/email and phone were recruited from clinic and randomized to one of eight study groups: Groups 1-6 completed the survey via Web, IVRS, and Paper, in one of six possible orders; Groups 7-8 completed the survey twice, either by Web or by IVRS.  The survey contained the 18-item Likert scale MSKCC Bowel Function Instrument (BFI) and single-item 11-point NRS LASA QOL. Surveys were completed from home, on consecutive days.  Mode equivalence was assessed by comparison of means across modes and intra-class correlation coefficients (ICC), and was compared to the test-retest reliability of Web and IVRS. RESULTS: Of 170 patients enrolled, 157 completed at least one survey and were included in analysis.  Patient sample (N=157) was mean age 56 (SD=11), 53% male, 81% white, 53% colon and 47% rectal cancer; 78% completed all assigned surveys. Mean scores for BFI total score, BFI subscale scores, and LASA QOL varied by mode by less than half a point. ICCs across mode were: BFI total score (Web-Paper=0.96, Web-IVRS=0.97, Paper-IVRS=0.97); BFI subscales (range=0.88 – 0.98); and LASA QOL (Web-Paper=0.98, Web-IVRS=0.78, Paper-IVRS=0.80). ICCs within mode (test-retest reliability) were: BFI total score (Web=0.97, IVRS=0.95); BFI subscales (range=0.73 – 0.95); and LASA QOL (Web=0.99, IVRS=0.49). CONCLUSIONS:  Mode equivalence for multiple-item scales was high (>0.88), and for single-item LASA QOL > 0.78, and is comparable to test-retest reliability. Whether collecting PRO data through one or multiple modes, to adequately power PRO endpoints, clinical trialists may increase sample size to account for observed measurement reliability.