Juvenile play behaviors in 21 day old female B6, LP/J, and BTBR inbred mice. One Way ANOVA revealed significant strains differences in (A) nose-to-nose sniffs (F2, 30=18.74, p<.0001), (B) following the play partner (F2.30=7.83, p<.01), (C) push-crawl play-soliciting attempts (F2,30=14.95, p<.0001), and (D) arena exploration (F2,30 =20.45, p<.0001). Scheffe post hoc tests revealed that LP/J scored lower than B6 on all four measures (p<.01 for each comparison) and lower than BTBR females on push-crawl and arena exploration (p<.01 for each comparison). BTBR females made fewer nose-to-nose sniffs than B6 (p<.01) and showed a trend toward reduced following. B6 N=12, LP/J N=15, BTBR N=9. * p<.01 versus B6; # p<.01 BTBR versus LP/J.