PCR amplification revealed length polymorphism of the 3′ region of the SSU rDNA gene among special forms of Fusarium solani. These length polymorphisms were found within each of F. solani f. sp. phaseoli, f. sp. batatas and f. sp. piperis. Nucleotide sequence analysis in this region detected intron-like sequences ranging in size from 408 to 439 bp and one 12 bp. The six 408 to 439 bp intron-like sequences were classified into types I-1 and I-2. The sequence similarity was high within I-1 or I-2 type sequences (84.8% and 81.1 to 92.8%, respectively) compared to that between I-1 and I-2 type sequences (45.7 to 48.5%). Both I-1 and I-2 type sequences had a specific insertion point in the SSU rDNA 3′ region. I-1 type sequences had the characteristics of group I introns: (1) a U at the 5′ splice site of the exon, (2) a G at the 3′ splice site of the intron, and (3) they contained the conserved sequence elements P, Q, R, and S. I-2 type sequences had characteristics: (1) and (2), but they did not have any characteristic (3). The 12 bp intron-like sequence was identical to the part of the 5′ end of I-2 type sequences, and its insertion point was the end of I-2 type sequences. The presence or absence of these intron-like sequences caused the length polymorphism of the SSU rDNA 3′ region of F. solani.