Estimates of immunization coverage in developing countries are typically made on a "card plushistory" basis, combining information obtained from vaccination cards with information frommothers' reports, for children for whom such cards are not available. A recent multi-round surveyin rural lower Egypt was able to test the accuracy of mothers' reports for a subset of childrenwhose cards were not seen at round 1 of the survey but were seen a year later at round 3.Comparisons of the unsubstantiated reports at round 1 with information recorded from cards seenat round 3 indicate that mothers' reports are of very high quality; mothers' reports at round 1 wereconfirmed by card data at round 3 for between 83 and 98 percent, depending on vaccine, ofchildren aged 12-23 and 24-35 months at round 3. The number of incorrect "Not Vaccinated"answers is higher than the number of incorrect "Vaccinated" responses, suggesting that, at leastin this setting, "card plus history" based estimates slightly underestimate true coverage levels.Most of the inconsistencies between round 1 and round 3 data apparently arose from intervieweror data processing error rather than from misreporting by mothers