Mode effects on responses to survey items may introduce bias to data collected using multiple modes of administration. The present study examines data from 704 surveys conducted as part of a longitudinal study in which parents and their children had been surveyed at multiple prior time points. Parents of 22-year-old study participants were randomly assigned to one of two mixed-mode conditions: (1) web mode first followed by the offer of an interviewer-administered telephone mode; or (2) telephone mode first followed by the offer of the web mode. Comparison of responses by assigned condition on 12 measures showed one statistically significant difference. Analyses that modeled differences by completed mode and the interaction between assigned condition and completed mode found significant differences on six measures related to completed mode. None of the differences indicated that more socially desirable responses were given in interviewer-administered surveys.