This study investigates the existence of the day-of-the-week, monthly and intra-month effects in pepper, garlic and onion markets, over the period from January 1992 through December 2003. The multiple regression model with the related dummy variables is estimated by ordinary least squares(OLS) to obtain the average vluae of daily logarithmic price changes. The day-of-the-week effect, where the average price changes are significantly higher or lower on some dyas of the week than others, is found in onion prices, with the pattern of positive price changes on Tuesday and negative price changes on Saturday. The monthly effect, where average price changes are much higher or lower in certain months of the year than in any other months, is clearly found in garlic prices, with average price changes being significantly positive in the winter(December, January and February) and the rainy season(August), and significantly negative in the harvesting season(May). The intra-month effect, where average price changes are much higher or lower in certain periods of the month than in any other periods, is found in garlic and onion prices, with average price changes during the first ten days of the month being significantly higher than during the second or third equivalent period of the monthly. The results imply that if these seasonal effects are persistent in their occurrence and magnitude, producers could develop marketing strategies which enhance their returns on the basis of such systematic patterns.