An adaptability and stability study was carried out using soybean yield data from several locations in Parana State, obtained from 1990 to 1999. The main objectives were: a) to check the efficiency of the Embrapa Soja breeding program for selecting the highest yielding lines with specific (regional) or broad adaptation; b) to analyze the performance of the control cultivars under favorable and unfavorable conditions; c) to identify the best stability methodology for inbred line evaluation. The evaluated lines were classified into early (L), semiearly (M) and medium (N) maturity groups. A randomized complete block design with four replications was used in each location and all analyses were carried out by maturity group. The number of M maturity lines that scored higher than the controls BR-16 and Embrapa 4 increased along the years, especially in unfavorable environments. On the other hand, the number of L and N maturity groups scoring higher than the controls either remained constant or fluctuated (increasing or decreasing) with time. The controls FT-Guaira, Embrapa 4, BR16 and FT-10 and the great majority of the tested lines showed broad adaptation. IAS 5 and FT-Abyara showed adaptation to poor environments and also broad adaptation. The analysis of the means in favorable and unfavorable environments was the most efficient method for soybean line evaluation. A methodology to classify soybean genotypes was proposed, based on these means.