Aim: Comparison of cancer mortality rates in four Greek counties during the decades 1979-1988 and 1989-1998 and drawing out of cause and effect relationships that could lead to organization of prevention programs. Methods: We used the Wilcoxon-White test to statistically compare data between the two decades as well as between the four counties separately. Results: We found that the total proportional mortality during the decade 1988-1998 significantly increased, compared to 1979-1988, in all

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... nties we studied. We noted a statistically significant increase of the proportional mortality of organs of the gastrointestinal tract and peritoneum (W = 55, p < 0.001 for both decades), of the respiratory system and intrathoracic organs (W = 71, p = 0.009 for 1979-1988 and W = 55, p < 0.001 for 1988-1998) and the skin and breast (W = 136, p = 0.019 for 1979-1988) in Attiki compared to Thessaloniki. As far as Achaia and Trikala are concerned, we found a minor, though statistically significant increase of the proportional mortality of organs of the gastrointestinal tract and peritoneum (W = 78, p = 0.043), of the respiratory system and intrathoracic organs (W = 77, p = 0.035) and the skin and breast (W = 76, p = 0.029) during the decade 1988-1998. Conclusions: Statistically significant differences were noted concerning the incidence rates between four different counties as well as between two different decades. Although genetic factors might partially explain our results, environmental factors seem to be the main culprits.