This paper reports on household size changes in the Cote d'Ivoire between 1985 and 1988 as evidenced by the Cote d'Ivoire Living Standards Survey (CILSS). The decline, from 8.31 to just 6.32, cannot be explained in terms of real-world changes alone, and so must be due also to either sampling bias or non-sampling errors. The paper identifies a change in sampling procedures as the most likely cause of the problem. The over-enumeration of large households in the early years of the survey is also reflected in dwelling size changes. However, observed declines in household size measured within the same sampling arrangement, and even within the same panel of households, suggest that there is also a real-world decline in household size in Cote d'Ivoire. The paper concludes that care must be taken in over-time and cross-section analyses with the CILSS data, and an appropriate re-weighting of the data is called for.