implies that the primordial density fluctuation is consistent with Gaussian random phase. Recently, Komatsu et al. (2003) have presented limits to the amplitude of non-Gaussian primordial fluctuations in the WMAP 1-year CMB maps by measuring the bispectrum and Minkowski functionals, and found that the WMAP data are consistent with Gaussian primordial fluctuations. Similar result has been obtained by Colley & Gott (2003), who independently have measured the genus, one of the Minkowski functionals, from the WMAP maps. Gaztañaga & Wagg (2003) and Gaztañaga et al. (2003) also have concluded that the WMAP maps are consistent with Gaussian fluctuations from the measurement of the three-point correlation function and the higher-order moment of the two-point correlations, respectively. On the other hand, Chiang et al. (2003) argue that non-Gaussian signature has been detected from the foreground-cleaned WMAP map produced by Tegmark, de Oliveira-Costa, & Hamilton (2003) using the phase mapping technique. However, it should be noted that their analysis has been done for the whole sky map whose Galactic plane region still has significant foreground contamination.

In this paper, we perform an independent test for the Gaussianity of the CMB anisotropy field using the WMAP 1-year maps by measuring the genus and the 