The use of standard methodology allows us to compare and to evaluate the data generated from samplers under general use. In aerobiological pollen monitoring, the most frequently slide sampling methods used are based on the selection of different number of longitudinal or transverse traverses and random fields, which represents a small proportion of the entire slide. The aim of this study is to evaluate possible methodological errors produced when the different pollen count methods are used in relation to the results obtained if the whole slide area was quantified. Moreover, the optimization of the counting method by selecting the best longitudinal or transverses traverses that reflect the more accurate counting in relation to the total pollen obtained when the total tape surface was done. Therefore, 113 slides recorded in 2008 at Ourense (NW Spain) differing in its pollen content, recollected time of the year and representation of the different pollen types were selected in this survey. A comparison between the 4 longitudinal traverses, the 12 transverse traverses, and the 493 random fields methods was evaluated. The average relative error and squared error were calculated for both, longitudinal and transverse traverses and the most accurate lines number for counting were selected. Finally, the three counting techniques were compared and significant differences were detected.