moreover, in ma w cases it; is very important not to deviate from certain linguis- tic standards in generation, in which case hand- crafted grammars give excellent control. how- ever, in other applications tbr nlg the variety of the output is much bigger, and the demands on the quality of the output somewhat less strin- gent. a typical example is nlg in the con- text of (interlingua- or transthr-based) machine translation. another reason for reb~xing the quality of the output may be that not enough time is available to develop a flfll grammar tbr a new target language in nlg. in all these cases, stochastic ("empiricist") methods pro- vide an alternative to hand-crafted ("rational- ist") approaches to nlg. to our knowledge, the first to use stochastic techniques in nlg were langkilde and knight (1998a) and (1998b). in this paper, we present fergus (flexible em- piricist/rationalist generation using syntax). fertgus follows langkilde and knights seminal work in using an n-gram language model, but; we augment it with a tree-based stochastic model and a traditional tree-based syntactic grammar. more recent work on aspects of stochastic gen- eration include (langkilde and knight, 2000), (malouf, 1999) and (ratnaparkhi, 2000). betbre we describe in more detail how we use stochastic models in nlg, we recall the basic tasks in nlg (rainbow and korelsky, 1992; re- iter, 1994). during text  p lanning,  content and structure of the target text; are determined to achieve the overall communicative goal. dur- ing sentence planning, linguistic means - in particular, lexical and syntactic means are de- termined to convey smaller pieces of meaning. l)uring real izat ion,  the specification chosen in sentence planning is transtbrmed into a surface string, by line~rizing and intlecting words in the sentence (and typically, adding function words). as in the work by langkilde and knight, our work ignores the text planning stage, but it; does address the sentence, planning and the realiza- tion stages. the structure of the paper is as tbllows.explo i t ing a probabi l ist ic  hierarchical mode l  for generat ion srinivas bangalore and owen rambow at&t labs research 180 park avenue f lorham park, nj 07932 {sr in?,  rambow}@research,  a r t .