Fusarium verticillioides is a common causal agent of maize ear rot in the Philippines. Eighty isolates were collected from healthy and infected maize cobs from Laguna province. Fifty isolates crossed with one of the mating type A testers. The ratio of MATA-1:MATA-2 is 27:23, which follows a Mendelian ratio of 1:1. The effective population number, Ne, was determined by mating type and male/hermaphrodite polymorphisms. The effective population number for mating type, Ne(mt), is 81% of the count (total population), and that for male/hermaphrodite status, Ne(f), is 36?42% of the count (total population). Sexual reproduction in Philippine isolates of F. verticillioides does not occur frequently, compared to F. verticillioides in other regions of the world.