Seasonality less likely to be consistent for specific stocks given all the different stock-specific events that can occur. Also, a major move in 1 or 2 years is also more likely to skew any historical look. Hirsch at Trader's Almanac does seasonal analysis on sectors, I believe. One might then use stocks within a particular sector if one so chooses, but that would be less reliable, I would think. For example, one might position in the OIH companies based on S/R and seasonality of oil.