Contacting a suitable respondent at home and securing the interview is a significant component of the typical house-hold telephone survey. An optimal calling schedule minimizes the number of callbacks required and thus conserves resources. This article presents an analysis of time-of-day and day-of-week effects on the probabilities of obtaining an answered outcome and an interviewed outcome in a large national telephone survey of adult males. The data presented indicate that, at least for the survey population included in this study, the chances of obtaining an answer and conducting an interview on the first call are much better on weekday evenings and on weekends than they are during weekday daytime hours. Moreover, there is some evidence to indicate that this findings also applies to second calls made to first-call no-answers, at least with regard to contacting efforts. Time-of-day and/or day-of-week effects on first call outcomes appear to be generally consistent with respect to both contacting and interviewing, although Sunday has a decidedly higher interview response rate for answered calls than do the other calling periods analyzed.