Abstract Older cockroach, Diploptera punctata, males (28 days old) transferred more sperm and larger spermatophores to females than 8-or 14-day-old males. In one male: one female behavioural tests, no significant correlations were found between either how rapidly males initiated courtship with females (response time), or intensity or duration of courtship, and the number of sperm or size of spermatophore subsequently transferred. Eight-day males were slower to initiate courtship than 28-day males. There was no significant differences in the duration of courtship for 8-, 14- and 28-day males, even though the mean duration of courtship was more than twice, as long for 8-day males compared with 14- and 28-day males. In competitive mating tests with one female and three males, one of each age, 28-day males were significantly more successful than 8- and 14-day males. It is concluded that the greater success of 28-day males is due to differences in male behaviour rather than to female discrimination.