This study examines the relationship between different types of conversational interactionand SLA. Long's (1996) updated version of the interactionist hypothesis claims thatimplicit negative feedback, which can be obtained through negotiated interaction, facilitatesSLA. Similar claims for the benefits of negotiation have been made by Pica (1994) and Gass(1997). Some support for the interaction hypothesis has been provided by studies that haveexplored the effects of interaction on production (Gass & Varonis, 1994), on lexicalacquisition (Ellis, Tanaka, & Yamazaki, 1994), on the short-term outcomes of pushedoutput (see Swain, 1995), and for specific interactional features such as recasts (Long, Inagaki,& Ortega, 1998; Mackey & Philp, 1998). However, other studies have not foundeffects for interaction on grammatical development (Loschky, 1994). The central questionaddressed by the current study was: Can conversational interaction facilitate second languagedevelopment? The study employed a pretest-posttest design. Adult ESL learners (N =34) of varying L1 backgrounds were divided into four experimental groups and one controlgroup. They took part in task-based interaction. Research questions focused on thedevelopmental outcomes of taking part in various types of interaction. Active participation ininteraction and the developmental level of the learner were considered. Results of this studysupport claims concerning a link between interaction and grammatical development andhighlight the importance of active participation in the interaction.