Distribution and growth of rainbow smelt Osmerus mordax larvae are described from samples collected in eastern Lake Michigan during 1978–1981 with plankton nets and benthic sleds deployed in water 1–15 m deep. Rainbow smelt larvae less than 25.5 mm total length were caught from May to early August, whereas young of the year 25.5 mm and larger occurred from July to September. Newly hatched larvae were found mostly during May; however, some hatching occurred in late June or early July, apparently due to slower incubation of eggs in deep cooler water. After hatching, rainbow smelt larvae were distributed in shallow water for a short period; from June to early August larvae were widely dispersed. Larvae concentrated inshore in late August. They generally were found at a few random depth strata from May to early August. In late August larvae concentrated near bottom. Larval rainbow smelt were most common at water temperatures of 10 to 16 C. Rainbow smelt averaged from 5.3 to 6.1 mm in May; they grew to a mean length of 15.7 mm after 1 month and to 36.5–41.1 mm after 3 months.