Multiclause sentences with the temporal adverbs "while" or "when" referring to simultaneous events (e.g., "While [when] John was writing a letter, Mary comes into the room") were compared in German and Spanish. Following Talmy (2001), we assumed that the event in the main clause is the figure (F; the event to be located in time), and the event in the adverbial clause is the ground (G; the event used as temporal reference). Germans judged as more acceptable the "while" ("wahrend") sentences with the longer duration event as G (e.g., writing a letter) and the shorter duration event as F (e.g., coming into the room) than vice versa. However, they judged "when" ("als") sentences quite acceptable in both duration conditions, suggesting that this adverb is temporally less constrained than "while." Spaniards produced a similar, although less conspicuous, pattern. We discuss the results in terms of the temporal metrics that underlie F-G relations in adverbial sentences, as well as crosslinguistic differences between Spanish and German. (Contains 3 footnotes and 9 tables.) [Preparation of this article was supported by an Integrated Action grant from the Spanish Ministry of Science and Technology and the German Academic Exchange Service.]