An experiment was carried out to determine the optimal recruitment strategy for a new online household panel. The factors to be optimized were contact mode, incentive amount, timing of the incentive, content of the advance letter, and timing of the panel participation request. The experimental design took into account the “naturally” varying factor of whether or not the households involved had a known fixed landline. Contact was made by either telephone (CATI) or face-to-face (CAPI). The results showed equivalent contact and recruitment rates for CATI and CAPI for households with a known telephone number. The contact rate was substantially lower for households without a known telephone number, even when controlling for the effect of contact mode. The response rates were not affected by the content of the advance letter. Response rates were also independent of whether the nature of the panel study was explained before or after the recruitment interview was completed. All incentives were found to have much stronger effects on response rates when they were distributed with the advance letter (prepaid) than when they were paid later (promised). The highest response rate was found with a prepaid incentive of 10 euros. The 20-euro and 50-euro incentives did not substantially increase response rates beyond those seen at the 10-euro level. Moreover, in comparison to the 20-euro and 50-euro prepaid incentives and to the promised incentives, the estimated costs per registered household were lowest for the prepaid 10-euro incentive.