OBJECTIVES: To determine whether the binary with follow-up (BWFU) or open-ended (OPED) contingent valuation question format would yield better valid estimates of altruistic willingness to pay (WTP) and examine the feasibility of using intra-community altruistic contributions to procure insecticide-treated nets (ITNs) for the poor in Nigeria. METHODS: Structured questionnaires were used to elicit stated altruistic WTP from a random sub-sample of respondents that had either the OPED or BWFU used to elicit WTP in Southeast Nigeria. One month after the survey the respondents were asked to redeem their WTP pledges. Construct validity was determined using econometric analyses, while phi correlation coefficient was used to determine criterion validity. FINDINGS: More than 57% of the respondents were hypothetically willing to pay for altruism in both BWFU and OPED groups. Altruistic WTP was positively related to respondents' WTP for own nets (p<0.01) and nets for other household members (p<0.05) in both groups. A total of 27.0% and 33.1% of the respondents with positive hypothetical WTP in the BWFU and OPED actually contributed. Phi correlation coefficient was 0.23 (95%CI 0.20-0.29) in BWFU and 0.49 (95%CI 0.44-0.54) in OPED. The money realised was used to buy some ITNs, which were presented to poor people selected by community leaders. CONCLUSION: The OPED elicited better valid estimates of altruistic WTP than BWFU. The potential for more capable people to contribute for the poor in ITNs programmes actually exist and malaria control programmes should explore altruistic contributions as a means to increase net coverage.